Constrain to +/- 2 octaves (+ semitones) as it's less demanding of block size; minor tidying

ladspa/RubberBandPitchShifter.h

@@ -102,6 +102,7 @@ protected:
 
     size_t m_blockSize;
     size_t m_reserve;
+    size_t m_bufsize;
     size_t m_minfill;
 
     RubberBand::RubberBandStretcher *m_stretcher;