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/gapplication.c

@@ -451,8 +451,6 @@ test_actions (void)
 int
 main (int argc, char **argv)
 {
-  g_type_init ();
-
   g_test_init (&argc, &argv, NULL);
 
   g_test_dbus_unset ();