Update libavfilter version check

Make the version check compatible with both ffmpeg and libav.
Also add comments describing when the API change was made for
both libraries.
[WIN32] fixed: setup file name got the branch name back.
Merge pull request #2597 from Alphix/ffmpeg-libav-fixes

ffmpeg and libav compatibility fixes
StringUtils::FindWords fix dead loop.
Merge pull request #2617 from ulion/fix_findword_deadloop

StringUtils::FindWords fix dead loop (introduced by PR #2536)
[win32] fixed: DX runtime setup was not included after 9eaf1cd
Merge pull request #2615 from a11599/buildsetupfix

[win32] fixed: DX runtime setup was not included after 9eaf1cd
demuxer ffmpeg: move m_streams into a map, drop MAX_STREAMS
dvdplayer: move extradata cleanup to CDVDDemuxStream destructor
dvdplayer: keep temporary stream pointer in ffmpeg AddStream
dvdplayer: keep ffmpeg demuxer indexes in continous order
demuxer ffmpeg: handle pmt changes
[ffmpeg] fix shared library versions
[Python] Adds autoclose to python's yesno dialog.
[Fix] Only start checking the nfo file from the first episodedetails tag
Allow dashes in music videos on the first pass
Merge pull request #2623 from ScudLee/NfoFileFix

[Fix] episode nfo with XML declaration and mismatched episode numbers would be ignored
[WIN32] fixed: setup file name got the branch name back (2. try)
[WIN32] fixed trailing space at the end of the branch name (I will do more tests...I will do more tests...I will do more tests...)
fix creation of new sources.xml (fixes #14272)