Remove VS2012 support.

LAV Filters requires VS2013 to build.
Update LAV Filters to 0.59.1-93-4cd23f1 (custom build based on 0.59.1-88-2b2c763).

Important changes:
 - LAV Splitter: Fix a crash when opening MKV files with big attachments (fixes #3862).
 - LAV Video: DXVA VC1/WMV3 decoding now works on Intel cards (fixes #3849).
Fix a possible dead lock when opening a file when one is already playing.

Easily reproducible with madVR.

Ticket #3865.