* include/vlc_codec.h: defines decoders/encoders related structures here.
* include/vlc_video.h: new video_frame_format_t structure which defines the properties of a video frame.
* include/vlc/decoder.h: include vlc_codec.h
* src/misc/objects.c: added VLC_OBJECT_PACKETIZER and VLC_OBJECT_ENCODER object types.
* modules/stream_out/transcode.c, modules/codec/theora.c: experimental theora video encoder.
* src/input/*: some cleanup.