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-peer.c

@@ -1801,7 +1801,6 @@ main (int   argc,
   GDBusNodeInfo *introspection_data = NULL;
   gchar *tmpdir = NULL;
 
-  g_type_init ();
   g_test_init (&argc, &argv, NULL);
 
   introspection_data = g_dbus_node_info_new_for_xml (test_interface_introspection_xml, NULL);