Rename to fuse_session_new_versioned

Rename to fuse_session_new_versioned

Similar previous renames to fuse_main_real_versioned,
but here for the low level fuse_session_new.
Also remove symbol versioned as part of "fuse_session_new"
as that function is not part of the official API/ABI
and to allow easier access with dlopen/dlsym.
Also switch back to a macro fuse_session_new, just in
case some code has some expectations on that.

Signed-off-by: Bernd Schubert <bernd@bsbernd.com>