Remove g_type_init() calls

Very many testcases, some GLib tools (resource compiler, etc) and
GApplication were calling g_type_init().

Remove those uses, as they are no longer required.

https://bugzilla.gnome.org/show_bug.cgi?id=686161

gio/tests/gdbus-connection-slow.c

@@ -194,7 +194,6 @@ int
 main (int   argc,
       char *argv[])
 {
-  g_type_init ();
   g_test_init (&argc, &argv, NULL);
 
   /* all the tests rely on a shared main loop */