fix a few warnings on non-Linux

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

gio/gsocketaddress.c

@@ -23,6 +23,7 @@
 
 #include <config.h>
 #include <glib.h>
+#include <string.h>
 
 #include "gsocketaddress.h"
 #include "ginetaddress.h"

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);

glib/gfileutils.c

@@ -1014,7 +1014,10 @@ write_to_temp_file (const gchar  *contents,
       }
   }
 #endif
+
+#ifdef BTRFS_SUPER_MAGIC
  no_fsync:
+#endif
   
   errno = 0;
   if (fclose (file) == EOF)

glib/tests/option-argv0.c

@@ -27,6 +27,7 @@
 #include <stdio.h>
 #include <string.h>
 
+#ifdef __linux
 static void
 test_platform_argv0 (void)
 {
@@ -45,6 +46,7 @@ test_platform_argv0 (void)
   g_assert (strcmp (g_get_prgname(), "option-argv0") == 0
 	    || strcmp (g_get_prgname (), "lt-option-argv0") == 0);
 }
+#endif
 
 int
 main (int   argc,