[osx] adapt AERingBuffer.h to allow planar formats
[osx] adapt OSX sink to utilise planar output from AE
[osx] drop the bitstreaming buffer - it's not much more costly than multiple small memcpy's and it's not as if we're performance constrained here
[osx] use a separate member for the frames per second in computations rather than m_format.m_sampleRate
[ios/osx] drop unused IsCompatible() functions from darwin audio sinks
Merge pull request #4774 from jmarshallnz/planar

[osx] utilize planar support from AE in the OSX sink