ext/theora/: Added first attempt at cropping of the image as required by the theora spec. We need more properties in ...

Original commit message from CVS:
* ext/theora/theoradec.c: (theora_get_formats),
(theora_dec_src_convert), (theora_dec_sink_convert),
(theora_dec_src_query), (theora_dec_src_event), (theora_dec_event),
(theora_dec_chain):
* ext/theora/theoraenc.c: (theora_enc_sink_link):
Added first attempt at cropping of the image as required by the
theora spec. We need more properties in the caps (offset_x,
offset_y,stride) to implement this correctly.
Added some debug info in the encoder. Note :the encoder is not
updated with the offset code.