codegen/: Updated codegen to support miniobject

codegen/: Updated codegen to support miniobject

Original commit message from CVS:
* codegen/argtypes.py:
* codegen/codegen.py:
* codegen/definitions.py:
* codegen/defsparser.py:
* codegen/defsconvert.py:
* codegen/docgen.py:
Updated codegen to support miniobject
* gst/Makefile.am:
Use the included (and modified) codegen for code generation.
* gst/pygstminiobject.c:
* gst/pygstminiobject.h:
* gst/pygstminiobject-private.h:
New GstMiniObject inspired from pygobject.[ch] code
* gst/common.h:
* gst/gst-types.defs:
* gst/gst.override:
* gst/gstbuffer.override:
* gst/gstcaps.override:
* gst/gstmodule.c:
* gst/gstpad.override:
Modifications to support MiniObject
* gst/gst.defs:
Allow null second parameter for ElementFactory.create()
and gst.element_factory_make()