Fix doxygen deprecation warning (#774)

Fix doxygen deprecation warning (#774)

Before:

```
$ doxygen doc/Doxyfile
warning: Tag 'COLS_IN_ALPHA_INDEX' at line 707 of file 'doc/Doxyfile' has become obsolete.
         To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u"
warning: Tag 'PERL_PATH' at line 1048 of file 'doc/Doxyfile' has become obsolete.
         To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u"
warning: Tag 'CLASS_DIAGRAMS' at line 1061 of file 'doc/Doxyfile' has become obsolete.
         To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u"
warning: Tag 'MSCGEN_PATH' at line 1070 of file 'doc/Doxyfile' has become obsolete.
         To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u"
warning: Tag 'DOT_TRANSPARENT' at line 1207 of file 'doc/Doxyfile' has become obsolete.
         To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u"
warning: Changing CLASS_GRAPH option to TEXT because obsolete option CLASS_DIAGRAM was found and set to NO.
/Users/matthias/prog/fuser/libfuse/include/fuse.h:934: warning: argument 'private_data' of command @param is not found in the argument list of fuse_new_31(struct fuse_args *args, const struct fuse_operations *op, size_t op_size, void *user_data)
/Users/matthias/prog/fuser/libfuse/include/fuse.h:934: warning: The following parameter of fuse_new_31(struct fuse_args *args, const struct fuse_operations *op, size_t op_size, void *user_data) is not documented:
  parameter 'user_data'
```

So let's try `doxygen -u doc/Doxyfile`.  After:

```
$ doxygen doc/Doxyfile
/Users/matthias/prog/fuser/libfuse/include/fuse.h:934: warning: argument 'private_data' of command @param is not found in the argument list of fuse_new_31(struct fuse_args *args, const struct fuse_operations *op, size_t op_size, void *user_data)
/Users/matthias/prog/fuser/libfuse/include/fuse.h:934: warning: The following parameter of fuse_new_31(struct fuse_args *args, const struct fuse_operations *op, size_t op_size, void *user_data) is not documented:
  parameter 'user_data'
```

The generated documentation `doc/html` does not differ.

For ease of review, here's a diff with all blank lines and comments removed via `grep -vE '^#|^$' doc/Doxyfile`

```
diff --git a/doc/Doxyfile.old b/doc/Doxyfile.new
index dbf469b..3f56d32 100644
--- a/doc/Doxyfile.old
+++ b/doc/Doxyfile.new
@@ -3,0 +4,2 @@ PROJECT_NUMBER         =
+PROJECT_BRIEF          =
+PROJECT_LOGO           =
@@ -5,0 +8,2 @@ CREATE_SUBDIRS         = NO
+CREATE_SUBDIRS_LEVEL   = 8
+ALLOW_UNICODE_NAMES    = NO
@@ -26,0 +31 @@ JAVADOC_AUTOBRIEF      = NO
+JAVADOC_BANNER         = NO
@@ -28,0 +34 @@ MULTILINE_CPP_IS_BRIEF = NO
+PYTHON_DOCSTRING       = YES
@@ -36,0 +43,5 @@ OPTIMIZE_OUTPUT_VHDL   = NO
+OPTIMIZE_OUTPUT_SLICE  = NO
+EXTENSION_MAPPING      =
+MARKDOWN_SUPPORT       = YES
+TOC_INCLUDE_HEADINGS   = 5
+AUTOLINK_SUPPORT       = YES
@@ -41,0 +53 @@ DISTRIBUTE_GROUP_DOC   = NO
+GROUP_NESTED_COMPOUNDS = NO
@@ -42,0 +55,2 @@ SUBGROUPING            = YES
+INLINE_GROUPED_CLASSES = NO
+INLINE_SIMPLE_STRUCTS  = NO
@@ -43,0 +58,2 @@ TYPEDEF_HIDES_STRUCT   = NO
+LOOKUP_CACHE_SIZE      = 0
+NUM_PROC_THREADS       = 1
@@ -45,0 +62,2 @@ EXTRACT_PRIVATE        = NO
+EXTRACT_PRIV_VIRTUAL   = NO
+EXTRACT_PACKAGE        = NO
@@ -49,0 +68 @@ EXTRACT_ANON_NSPACES   = NO
+RESOLVE_UNNAMED_PARAMS = YES
@@ -56,0 +76,2 @@ HIDE_SCOPE_NAMES       = NO
+HIDE_COMPOUND_REFERENCE= NO
+SHOW_HEADERFILE        = YES
@@ -57,0 +79,2 @@ SHOW_INCLUDE_FILES     = YES
+SHOW_GROUPED_MEMB_INC  = NO
+FORCE_LOCAL_INCLUDES   = NO
@@ -60,0 +84 @@ SORT_BRIEF_DOCS        = NO
+SORT_MEMBERS_CTORS_1ST = NO
@@ -62,0 +87 @@ SORT_BY_SCOPE_NAME     = NO
+STRICT_PROTO_MATCHING  = NO
@@ -72,0 +98,2 @@ FILE_VERSION_FILTER    =
+LAYOUT_FILE            =
+CITE_BIB_FILES         =
@@ -76,0 +104 @@ WARN_IF_DOC_ERROR      = YES
+WARN_IF_INCOMPLETE_DOC = YES
@@ -77,0 +106,2 @@ WARN_NO_PARAMDOC       = NO
+WARN_IF_UNDOC_ENUM_VAL = NO
+WARN_AS_ERROR          = NO
@@ -78,0 +109 @@ WARN_FORMAT            = "$file:$line: $text"
+WARN_LINE_FORMAT       = "at line $line of file $file"
@@ -82 +113,5 @@ INPUT_ENCODING         = UTF-8
-FILE_PATTERNS          = *.h *.c *.h *.dox
+INPUT_FILE_ENCODING    =
+FILE_PATTERNS          = *.h \
+                         *.c \
+                         *.h \
+                         *.dox
@@ -89 +124,2 @@ EXAMPLE_PATH           = example
-EXAMPLE_PATTERNS       = *.c *.h
+EXAMPLE_PATTERNS       = *.c \
+                         *.h
@@ -94,0 +131,3 @@ FILTER_SOURCE_FILES    = NO
+FILTER_SOURCE_PATTERNS =
+USE_MDFILE_AS_MAINPAGE =
+FORTRAN_COMMENT_AFTER  = 72
@@ -100,0 +140 @@ REFERENCES_LINK_SOURCE = YES
+SOURCE_TOOLTIPS        = YES
@@ -104 +143,0 @@ ALPHABETICAL_INDEX     = NO
-COLS_IN_ALPHA_INDEX    = 5
@@ -112 +151,10 @@ HTML_STYLESHEET        =
-GENERATE_HTMLHELP      = NO
+HTML_EXTRA_STYLESHEET  =
+HTML_EXTRA_FILES       = doc/fast17-vangoor.pdf
+HTML_COLORSTYLE        = AUTO_LIGHT
+HTML_COLORSTYLE_HUE    = 220
+HTML_COLORSTYLE_SAT    = 100
+HTML_COLORSTYLE_GAMMA  = 80
+HTML_TIMESTAMP         = NO
+HTML_DYNAMIC_MENUS     = YES
+HTML_DYNAMIC_SECTIONS  = YES
+HTML_INDEX_NUM_ENTRIES = 100
@@ -114,0 +163 @@ DOCSET_FEEDNAME        = "Doxygen generated docs"
+DOCSET_FEEDURL         =
@@ -116,2 +165,3 @@ DOCSET_BUNDLE_ID       = org.doxygen.Project
-HTML_DYNAMIC_SECTIONS  = YES
-HTML_EXTRA_FILES = doc/fast17-vangoor.pdf
+DOCSET_PUBLISHER_ID    = org.doxygen.Publisher
+DOCSET_PUBLISHER_NAME  = Publisher
+GENERATE_HTMLHELP      = NO
@@ -123,0 +174,10 @@ TOC_EXPAND             = NO
+GENERATE_QHP           = NO
+QCH_FILE               =
+QHP_NAMESPACE          = org.doxygen.Project
+QHP_VIRTUAL_FOLDER     = doc
+QHP_CUST_FILTER_NAME   =
+QHP_CUST_FILTER_ATTRS  =
+QHP_SECT_FILTER_ATTRS  =
+QHG_LOCATION           =
+GENERATE_ECLIPSEHELP   = NO
+ECLIPSE_DOC_ID         = org.doxygen.Project
@@ -125 +184,0 @@ DISABLE_INDEX          = NO
-ENUM_VALUES_PER_LINE   = 4
@@ -126,0 +186,2 @@ GENERATE_TREEVIEW      = NO
+FULL_SIDEBAR           = NO
+ENUM_VALUES_PER_LINE   = 4
@@ -127,0 +189,3 @@ TREEVIEW_WIDTH         = 250
+EXT_LINKS_IN_WINDOW    = NO
+OBFUSCATE_EMAILS       = YES
+HTML_FORMULA_FORMAT    = png
@@ -128,0 +193,14 @@ FORMULA_FONTSIZE       = 10
+FORMULA_MACROFILE      =
+USE_MATHJAX            = NO
+MATHJAX_VERSION        = MathJax_2
+MATHJAX_FORMAT         = HTML-CSS
+MATHJAX_RELPATH        =
+MATHJAX_EXTENSIONS     =
+MATHJAX_CODEFILE       =
+SEARCHENGINE           = NO
+SERVER_BASED_SEARCH    = NO
+EXTERNAL_SEARCH        = NO
+SEARCHENGINE_URL       =
+SEARCHDATA_FILE        = searchdata.xml
+EXTERNAL_SEARCH_ID     =
+EXTRA_SEARCH_MAPPINGS  =
@@ -129,0 +208,18 @@ GENERATE_LATEX         = NO
+LATEX_OUTPUT           = latex
+LATEX_CMD_NAME         =
+MAKEINDEX_CMD_NAME     = makeindex
+LATEX_MAKEINDEX_CMD    = makeindex
+COMPACT_LATEX          = NO
+PAPER_TYPE             = a4
+EXTRA_PACKAGES         =
+LATEX_HEADER           =
+LATEX_FOOTER           =
+LATEX_EXTRA_STYLESHEET =
+LATEX_EXTRA_FILES      =
+PDF_HYPERLINKS         = YES
+USE_PDFLATEX           = YES
+LATEX_BATCHMODE        = NO
+LATEX_HIDE_INDICES     = NO
+LATEX_BIB_STYLE        = plain
+LATEX_TIMESTAMP        = NO
+LATEX_EMOJI_DIRECTORY  =
@@ -130,0 +227,5 @@ GENERATE_RTF           = NO
+RTF_OUTPUT             = rtf
+COMPACT_RTF            = NO
+RTF_HYPERLINKS         = NO
+RTF_STYLESHEET_FILE    =
+RTF_EXTENSIONS_FILE    =
@@ -131,0 +233,4 @@ GENERATE_MAN           = NO
+MAN_OUTPUT             = man
+MAN_EXTENSION          = .3
+MAN_SUBDIR             =
+MAN_LINKS              = NO
@@ -132,0 +238,5 @@ GENERATE_XML           = NO
+XML_OUTPUT             = xml
+XML_PROGRAMLISTING     = YES
+XML_NS_MEMB_FILE_SCOPE = NO
+GENERATE_DOCBOOK       = NO
+DOCBOOK_OUTPUT         = docbook
@@ -134,0 +245,3 @@ GENERATE_PERLMOD       = NO
+PERLMOD_LATEX          = NO
+PERLMOD_PRETTY         = YES
+PERLMOD_MAKEVAR_PREFIX =
@@ -148,3 +261,2 @@ EXTERNAL_GROUPS        = YES
-PERL_PATH              = /usr/bin/perl
-CLASS_DIAGRAMS         = NO
-MSCGEN_PATH            =
+EXTERNAL_PAGES         = YES
+DIA_PATH               =
@@ -152,0 +265,4 @@ HAVE_DOT               = NO
+DOT_NUM_THREADS        = 0
+DOT_COMMON_ATTR        = "fontname=Helvetica,fontsize=10"
+DOT_EDGE_ATTR          = "labelfontname=Helvetica,labelfontsize=10"
+DOT_NODE_ATTR          = "shape=box,height=0.2,width=0.4"
@@ -154 +270 @@ DOT_FONTPATH           =
-CLASS_GRAPH            = YES
+CLASS_GRAPH            = TEXT
@@ -157,0 +274,3 @@ UML_LOOK               = NO
+UML_LIMIT_NUM_FIELDS   = 10
+DOT_UML_DETAILS        = NO
+DOT_WRAP_THRESHOLD     = 17
@@ -164,0 +284 @@ DIRECTORY_GRAPH        = YES
+DIR_GRAPH_MAX_DEPTH    = 1
@@ -165,0 +286 @@ DOT_IMAGE_FORMAT       = png
+INTERACTIVE_SVG        = NO
@@ -167,0 +289,5 @@ DOTFILE_DIRS           =
+MSCFILE_DIRS           =
+DIAFILE_DIRS           =
+PLANTUML_JAR_PATH      =
+PLANTUML_CFG_FILE      =
+PLANTUML_INCLUDE_PATH  =
@@ -170 +295,0 @@ MAX_DOT_GRAPH_DEPTH    = 1000
-DOT_TRANSPARENT        = NO
@@ -174 +298,0 @@ DOT_CLEANUP            = YES
-SEARCHENGINE           = NO
```