Original commit message from CVS:
* gst/gstbuffer.h:
Avoid unneeded type checking.
API: GST_BUFFER_IS_DISCONT
* gst/gstminiobject.h:
Avoid type check in flag accessor.
* gst/gstelementfactory.h:
* gst/gstplugin.h:
* gst/gstpluginfeature.h:
Add _CAST macros.
API: GST_ELEMENT_FACTORY_CAST
API: GST_PLUGIN_CAST
API: GST_PLUGIN_FEATURE_CAST