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-serialization.c

@@ -1056,7 +1056,6 @@ main (int   argc,
 {
   setlocale (LC_ALL, "C");
 
-  g_type_init ();
   g_test_init (&argc, &argv, NULL);
   g_test_bug_base ("https://bugzilla.gnome.org/show_bug.cgi?id=");