#serial 5# Define some macros required for proper operation of code in lib/*.c# on MSDOS/Windows systems.# From Jim Meyering.AC_DEFUN([jm_AC_DOS],  [    AC_CACHE_CHECK([whether system is Windows or MSDOS], [ac_cv_win_or_dos],      [        AC_TRY_COMPILE([],        [#if !defined _WIN32 && !defined __WIN32__ && !defined __MSDOS__neither MSDOS nor Windows#endif],        [ac_cv_win_or_dos=yes],        [ac_cv_win_or_dos=no])      ])    if test x"$ac_cv_win_or_dos" = xyes; then      ac_fs_accepts_drive_letter_prefix=1      ac_fs_backslash_is_file_name_separator=1    else      ac_fs_accepts_drive_letter_prefix=0      ac_fs_backslash_is_file_name_separator=0    fi    AH_VERBATIM(FILESYSTEM_PREFIX_LEN,    [#if FILESYSTEM_ACCEPTS_DRIVE_LETTER_PREFIX# define FILESYSTEM_PREFIX_LEN(Filename) \  ((Filename)[0] && (Filename)[1] == ':' ? 2 : 0)#else# define FILESYSTEM_PREFIX_LEN(Filename) 0#endif])    AC_DEFINE_UNQUOTED([FILESYSTEM_ACCEPTS_DRIVE_LETTER_PREFIX],      $ac_fs_accepts_drive_letter_prefix,      [Define on systems for which file names may have a so-called       `drive letter' prefix, define this to compute the length of that       prefix, including the colon.])    AH_VERBATIM(ISSLASH,    [#if FILESYSTEM_BACKSLASH_IS_FILE_NAME_SEPARATOR# define ISSLASH(C) ((C) == '/' || (C) == '\\')#else# define ISSLASH(C) ((C) == '/')#endif])    AC_DEFINE_UNQUOTED([FILESYSTEM_BACKSLASH_IS_FILE_NAME_SEPARATOR],      $ac_fs_backslash_is_file_name_separator,      [Define if the backslash character may also serve as a file name       component separator.])  ])