[osx] adapt AERingBuffer.h to allow planar formats
[EPG] Do *Persist*() calls on a copy of m_epgs

We can get in a situation where PersistAll() and PersistTables() are
running simutaneously, leading to memory corruption.
[EPG] Make sure we catch requests to update during update.
[PVR] Allow PVR subwindows access to real windows control ID
[PVR] Allow PVR subwindows to receive GUI messages
[PVR] Defer EPG notifications to app thread

Fixes deadlock opening liveTV window while channel EPGs are being
generated.