CONTRIBUTING.md: fix forking link.
Updated Czech translation
Spelling correction in Spanish translation.
Add some helper functions to check if a string matches an ISO 639 code or language.
Play > Subtitles menu: Improve the external subtitles naming.

Show the subtitle filename and detect the language whenever possible.
Sync mplayer.eu.rc.txt after 3c79306a0eca973bcb72061531b680d0d185d809.

Missing string in 8608c253a918f63586d88d3ed7bb285924957163 reappeared here...
DSUtil: Replace inline assembler by a compiler intrinsic.

This commits works around AStyle being fool by the non-standard __asm keyword.
Fix some implicit int64 to int32 conversion.
custom_messages.iss: updated Chinese Simplified translation.
Remove unused code.
Update Changelog.txt.
Updated Basque translation (ticket #2890).
Updated French translation.
Updated Polish translation.
Updated simplified Chinese translation.
Updated German translation.
Update LAV Filters to version 0.58.2-45-gf93cb2e

Important changes:
 - This update fixes an issue with LAV Audio Decoder mixer feature (fixes #3348).
 - This update fixes an issue with LAV Video Decoder where some Xvid files showed corruption (fixes #3368).
 - LAV Splitter can now connect to the VTS Reader source filter (used to open IFO files).
build_lavfilters.bat: Ensure compilation failures are properly detected.
ShockwaveGraph: restore process volume on exit

Applies to Vista and later.
Fixes #2852
Rewritten code for auto-load subtitles and support for '_' as a separator.

Being a video file named video.ext, video_whatever.srt will now be auto-loaded.

This commit fixes #3195.