Deprecate av_parse_video_frame_size() and av_parse_video_frame_rate()

Deprecate av_parse_video_frame_size() and av_parse_video_frame_rate()
in favor of the newly added corresponding functions
av_parse_video_size() and av_parse_video_rate() defined in
libavcore/parseutils.h.

This change also adds a linking-time dependency of libavcodec and of
libavfilter on libavcore.

Originally committed as revision 24518 to svn://svn.ffmpeg.org/ffmpeg/trunk