Draft: add edge264 decoder

This is a Work In Progress branch with H264 decoding through edge264. It may be useful to decode MVC which we don't support right now. Given we have to copy frames from the decoder we could output the MVC as side by side which is easier to handle in the display.

Current status:

• decodes a few frames and then deadlocks
• doesn't support passing timestamps to frames (since we only send NAL data)
• requires copying decoded data to a VLC picture (the borrow system doesn't seem to be made for that)
• MVC decoding doesn't detect the MVC part on a test Blu-ray (but in may be due to some missing Blu-ray support on our side)
• doesn't seem to support draining or flushing (or discontinuities)
• crashes when using 0 or 1 thread
• uses pthread_cancel() which is not available in Android
• doesn't support 32-bit arm (uses arm64 instructions)