codegen/: Updated codegenerator to current pygtk one.

codegen/: Updated codegenerator to current pygtk one.

Original commit message from CVS:
* codegen/Makefile.am:
* codegen/argtypes.py:
* codegen/codegen.py:
* codegen/definitions.py:
* codegen/defsconvert.py:
* codegen/defsparser.py:
* codegen/docextract.py:
* codegen/docextract_to_xml.py:
* codegen/docgen.py:
* codegen/h2def.py:
* codegen/mergedefs.py:
* codegen/missingdefs.py:
* codegen/mkskel.py:
* codegen/override.py:
* codegen/reversewrapper.py:
Updated codegenerator to current pygtk one.
* gst/gst.defs:
* gst/gst.override:
* gst/gstpad.override:
Update defs for new constructor definition.
* testsuite/test_bin.py:
With new constructors, pygobject will try to convert the argument to the
proper GType (here a string).