[PiSink] Fix some issues with buffering and multichannel

Also support AE_FMT_FLOAT and AE_FMT_S32 (requires updated firmware)
Buffer is increased to 100ms to reduce chance of underrun.
[dvdplayer] Use inexact seeking like omxplayer
[omxplayer] Make use of TrueHD fastpath when downmixing

The TrueHD codec actually works in 3 stages. It decodes the downmixed stereo. It then decodes the differences required to produce 5.1.
It then decodes the differences required to produce 7.1.

Many users end up downmixing this 7.1 stream back to 2.0.
Much better to tell the codec we only need the 2.0 stream. It saves about 50% of the CPU required
[omxplayer] When in dual audio mode, make one output the slave

May help audio sync between the two outputs
- ensure to announce airtunes before airplay via zeroconf (makes it more likely that ios7 clients detect us correctly at the first shot)
- add method to reannounce already published services
- reannounce airplay service every 10 secs (fixes ios7 clients not detecting us when their wlan was asleep or they saw the airplay announcement before the airtunes annoncement)
[rbp] Initial hacking aimed at getting hw accelerated resampling working

Not complete!
Revert "[rbp] Initial hacking aimed at getting hw accelerated resampling working"

This reverts commit 7e48ce51dc338b967a38504eb24815f1843efb5f.
AE: fix CAEChannelInfo::ResolveChannels, it returned duplicate channels in the list
[PiSink] Make side channels appear at back rather than front