Fix broken save of multiopt settings in javascript

Fixes #1751
hls: Add pointer to an interesting document about buffer mamangement in HLS
Log number of CPU cores during startup
android: Detect number of CPU cores
Add libyuv revision 775
android: Build for NEON and include libyuv
android: Add SW video playback + fix various other issues

- Video rendering using Surfaces and ANativeWindow

- More work on the prop <-> JNI bridge

- Better way of restarting UI due to configuration change (screen rotation)

- Extract AV clock from audio playback