Add G_UNLIKELY in type registration.

Add G_UNLIKELY in type registration.

Original commit message from CVS:
* gst/gsterror.c: (gst_g_error_get_type):
* gst/gstpadtemplate.c: (gst_pad_template_get_type),
(gst_static_pad_template_get_type):
* gst/gsttaglist.c: (gst_tag_list_get_type):
* gst/gsttagsetter.c: (gst_tag_setter_get_type):
* gst/gsttypefindfactory.c: (gst_type_find_factory_get_type):
* gst/gsturi.c: (gst_uri_handler_get_type):
* gst/gstvalue.c: (gst_date_get_type):
* gst/gstxml.c: (gst_xml_get_type):
* libs/gst/base/gstbasesink.c: (gst_base_sink_get_type),
(gst_base_sink_preroll_object), (gst_base_sink_get_position):
* libs/gst/base/gstbasesrc.c: (gst_base_src_get_type):
Add G_UNLIKELY in type registration.