preprocess: "assign PARSE_FLAG_ASM_COMMENTS only for asm files"

preprocess: "assign PARSE_FLAG_ASM_COMMENTS only for asm files"

    resolve a problem with the following test.c program, tcc -E test.c

    #ifdef	_XOPEN_SOURCE
    # define __USE_XOPEN	1
    # if (_XOPEN_SOURCE - 0) >= 500
    #  define __USE_XOPEN_EXTENDED	1
    #  define __USE_UNIX98	1
    #  undef _LARGEFILE_SOURCE
    #  define _LARGEFILE_SOURCE	1
    #  if (_XOPEN_SOURCE - 0) >= 600
    #   define __USE_XOPEN2K	1
    #   undef __USE_ISOC99
    #   define __USE_ISOC99		1
    #  endif
    # else
    #  ifdef _XOPEN_SOURCE_EXTENDED
    #   define __USE_XOPEN_EXTENDED	1
    #  endif
    # endif
    #endif

    int main() {}

    // # 17 "aaa.c"
    // aaa.c:17: error: #endif without matching #if