Update ffmpeg
Fix speex build without pkgconfig
Fix bpp handling
Update ffmpeg for ProRes 4K in MKV fix

Fixes issue 471.
Make HEVC AnnexB check a bit more lenient

Fixes issue 475
Update ffmpeg for HEVC SIMD backports
Enable crypto protocol

This allows playing AES encrypted HLS streams
[MPC-HC] Use our own ffmpeg clone repository.

WARNING: This should be the first custom commit in our fork and its title should not be modified.
[MPC-HC] LAV Splitter: Exhibits MKV attachments through IDSMResourceBag interface.
[MPC-HC] Tray icon: Add an optional custom callback for "show property page" events.
[MPC-HC] Fix the include directories for FFmpeg's out-of-source-tree build.
[MPC-HC] Version number: Add a "git describe based" commit number to identify the vanilla LAV Filters we are based on.

This way if we distribute LAV Filters version X.Y.Z.N, it means that our custom build is based on:
 - the stable version X.Y.Z,
 - with N official patches (which will be part of next official LAV Filters build),
 - and some custom non-official patches which are here to improve the integration in MPC-HC.