g_type_class_ref() other types as well, see #349410 and #64764.

g_type_class_ref() other types as well, see #349410 and #64764.

Original commit message from CVS:
* gst/gst.c: (init_post):
* gst/gstevent.c: (_gst_event_initialize):
* gst/gstquery.c: (_gst_query_initialize):
* libs/gst/dataprotocol/dataprotocol.c (gst_dp_init):
g_type_class_ref() other types as well, see #349410 and #64764.
* gst/gstbuffer.c: (_gst_buffer_initialize):
* gst/gstmessage.c: (_gst_message_initialize):
Simplify existing g_type_class_ref().