trancode: fix time_base and pkt_sri for audio, other cosmetic updates
global headers: create own AAC/MP4A header only if a valid does not exist
libav muxer: add AVMATROSKA muxer type
WebTV: Attempt at providing touchscreen-compatible navigation
WebTV: Attempt at providing touchscreen-compatible navigation part 2
Attempt at providing touchscreen-compatible navigation part 3 - scrolling channel list