Added 'keeprefcount' argument for function/method parameters in order to cope with functions/methods that decrement t...

Original commit message from CVS:
* codegen/argtypes.py:
* codegen/codegen.py:
* codegen/definitions.py:
* gst/arg-types.py:
Added 'keeprefcount' argument for function/method parameters in order to
cope with functions/methods that decrement the refcount of the given
parameter
* gst/gst.defs:
Added 'keeprefcount' for buffer argument of gst_pad_push() wrapper.