Add a lexer for JSON

Add a lexer for JSON

Our JSON parser is a three stage parser.  The first stage tokenizes the stream
into a set of lexical tokens.  Since the lexical grammar is regular, we can
use a finite state machine to model it.  The state machine will emit tokens
as they are identified.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>