CHG: Refactor ffmpeg MT support
Merge pull request #5200 from koying/chgffmpegmt

CHG: Refactor ffmpeg MT support
ffmpeg: bump to 2.4
ffmpeg: adapt win32 dlls to major versions of 2.4
[dvdplayer] Fix for timestamp correction when no audio or no video

If audio or video track is missing, we don't have to wait for the other track to have a matching timestamp jump
Also compare dts rather than correction values as suggested by FernetMenta
Merge pull request #5345 from popcornmix/correctioncorrectioncorrection

[dvdplayer] Fix for timestamp correction when no audio or no video
Merge pull request #5371 from FernetMenta/ffmpeg24

ffmpeg: bump to 2.4
dxva: fix and rework video surface handling
dxva: let renderer control the render buffers
dxva: flush ffmpeg buffers if it holds any refs on close
renderer: rename/correct GetProcessorSize, processor is not exposed anymore