Use hierarchic names convention (prefix them with av_expr) for theeval API.
More grep-friendly and more consistent with the rest of the FFmpegAPI.
Originally committed as revision 25708 to svn://svn.ffmpeg.org/ffmpeg/trunk
Add setpts filter, ported from the libavfilter soc repo.
Originally committed as revision 25655 to svn://svn.ffmpeg.org/ffmpeg/trunk