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/tls-certificate.c

@@ -269,7 +269,6 @@ main (int   argc,
   Reference ref;
   GError *error = NULL;
 
-  g_type_init ();
   g_test_init (&argc, &argv, NULL);
 
   _g_test_tls_backend_get_type ();