Merge changes from gnulib. This was prompted because the CVS

snapshot of Bison didn't build on Solaris 7 due to strnlen problems.

m4/dos.m4

@@ -0,0 +1,53 @@
+#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.])
+  ])