Added video stream interface in vid_stream.h, the video stream will be able to handle different video formats in encoding and decoding direction.
Renamed video device stream class identifiers from 'pjmedia_vid_stream*' to 'pjmedia_vid_dev_stream*' as 'pjmedia_vid_stream' is used by video stream interface.
Added ffmpeg video capability to be able to parse SDP format param for H263 and also decide video format for encoding direction based on remote preference and local format-capability setting.
Added some new APIs in jitter buffer for handling video stream: pjmedia_jbuf_put_frame3(), pjmedia_jbuf_get_frame3(), pjmedia_jbuf_peek_frame(), and pjmedia_jbuf_remove_frame().
Moved pjmedia_stream_info_from_sdp() from session to stream