stb_c_lexer.h: STB_C_LEX_C_IDENTIFIERS macro definition is not used.

[kevreco]

STB_C_LEX_C_IDENTIFIERS is defined with a Y but I can't see it used anywhere.

#define STB_C_LEX_C_IDENTIFIERS     Y   //  "[_a-zA-Z][_a-zA-Z0-9]*"               CLEX_id

There are other non-used macro definition but there are mentioned in the documentation:

// Status:
//     - haven't tested compiling as C++
//     - haven't tested the float parsing path
//     - haven't tested the non-default-config paths (e.g. non-stdlib)
//     - only tested default-config paths by eyeballing output of self-parse
//
//     - haven't implemented multiline strings
//     - haven't implemented octal/hex character constants
//     - haven't implemented support for unicode CLEX_char
//     - need to expand error reporting so you don't just get "CLEX_parse_error"

I might miss something but since it appeared to be a bit odd I created this issue.