gst/gst.defs: Update for new API

gst/gst.defs: Update for new API

Original commit message from CVS:
* gst/gst.defs:
Update for new API
* gst/gst.override:
Added unreffing for gst.Registry.get_plugin_list and .get_feature_list
* testsuite/common.py:
removed crude hack for gst.Registry and gst.Plugin
* testsuite/test_interface.py:
* testsuite/test_caps.py:
* testsuite/test_struct.py:
* testsuite/test_xml.py:
converted to using common's TestCase class
* testsuite/test_event.py:
Enabled/fixed previously non working test
* testsuite/test_registry.py:
Now uses common's TestCase class,
added special case setUp()