firmware: image_encode: Fix that works for both buffers and tunnelling.
See: http://forum.xbmc.org/showthread.php?tid=176043&pid=1673527#pid1673527

firmware: video_decode: Allow ts fifo to be forced off with avoid_fix_ts=2
See: http://forum.xbmc.org/showthread.php?tid=148646&pid=1674875#pid1674875

userland: tvservice: Enhance callback mechanism
See: https://github.com/raspberrypi/userland/pull/162