RTAS side-chain patch

Here are patches to add RTAS side-chain support to JUCE:






Feel free to use / merge to JUCE / etc.

Cheers, Yair

Just to make it more clear this patch resolves the following:

- RTAS now works with new just Bus Arrangment,

bool setPreferredBusArrangement (bool isInputBus, int busIdx, const AudioChannelSet& preferredLayout)

(it was making compile errors)

- Side-Chain seems to be properly working under Pro Tools RTAS (tested with Pro Tools 9 Mac/PC)