Properly handle d3dfs mouse capture and leave
VideoRenderers: comment out asserts from 8d2b621

I wouldn't dare to add locks there so close to the stable
MainFrame: override default MFC Alt key behavior

Refs #3956
Fix: Update the chapter marks on the seekbar when the media length changes.

Mostly useful for MKV with multiple editions.

Fixes #3963.
Update translations from Transifex:

 - Greek.