potential for bugginess in JackIO::ProcessCallback() if frameN has rolled over implicitly at RecordBufferSize for a base loop

[bill-auger]

this could result in endFrameN < beginFrameN

this is currently guarded against with the following caveat:

1. beginFrameN is fixed
2. triggers are ignored unless
   currentFrameN >= beginFrameN + (SampleRate * MINIMUM_LOOP_DURATION)

TODO: when base loop (endFrameN <= beginFrameN) copy beginFrameN upto RolloverFrameN then 0 upto endFrameN