fix a few warnings on non-Linux

mostly #ifdeffing functions that are only called by #ifdeffed code

gio/xdgmime/xdgmimemagic.c

@@ -479,7 +479,9 @@ _xdg_mime_magic_parse_magic_line (FILE              *magic_file,
       /* We clean up the matchlet, byte swapping if needed */
       if (matchlet->word_size > 1)
 	{
+#if LITTLE_ENDIAN
 	  int i;
+#endif
 	  if (matchlet->value_length % matchlet->word_size != 0)
 	    {
 	      _xdg_mime_magic_matchlet_free (matchlet);