External PGS subtitles: Fail nicely when a file can't be opened.

This commit fixes #4363.
Fix drag-and-drop from some applications.

Drag-and-dropping a downloaded file from Chrome failed for example.

This commit fixes #3036.
Update translations from Transifex:

 - Basque
 - British English
 - Catalan
 - Chinese (simplified)
 - Croatian
 - French
 - Galician
 - German
 - Greek
 - Italian
 - Japanese
 - Korean
 - Polish
 - Portuguese (Brazil)
 - Slovak
 - Spanish
 - Tatar
 - Turkish
 - Vietnamese
Fix GCD computation for negative values and support all integral types.

Using the GCD function on negative numbers caused an infinite loop, instead return the greatest positive common factor.

Fixes #4285.
EVR-CP and Sync renderers: Correctly compute the aspect ratio.

Use 64-bit unsigned integer to avoid overflows.

Fixes #4285.
Updated LAV Filters to 0.61.2-36-a6bd936 (custom build based on 0.61.2-31-0c8c081)

Important changes:
 - LAV Video: Fix some performance regressions introduced in v0.61 (mostly visible on old operating systems like Windows XP) (fixes #4357).
 - Use Win32 threads instead of pthreads.
 - Updated ffmpeg and libbluray.
Fix some CPPCheck warnings.
Thumbnails: Show an error message when the thumbnails would be too small.
Don't update the last window position when the option is disabled.

Avoid always modifying the settings for those who sync them.

Fixes #4377.
VSFilter: Add Dark Souls 1 to the blacklist.

http://forums.steampowered.com/forums/showthread.php?p=35530514
Fix compilation after f7b865a90114ac2b365a470239a36d542fa67436.

Rule N of Murphy's Law: If you forget to recompile just before pushing then the code is almost certainly broken due to a last minute change...

Also fix the changelog while at it.
Remove trailing spaces.