[pvoc] add missing aubio_pvoc_get_hop/win
src/spectral/phasevoc.h: add _set_window
src/spectral/phasevoc.c: fix error string
src/spectral/phasevoc.c: abort if fft creation failed
src/spectral/phasevoc.c: perfect reconstruction for overlap = 50% without modifications
src/spectral/phasevoc.c: set scaling to 1./3 if hop_s = win_s / 8, .5 otherwise
src/spectral/phasevoc.c: fix scaling factor for win_s = 4 * hop_s
src/spectral/phasevoc.c: apply windowing to resynthesized grain
src/, examples/: #ifdef HAVE_, not #if HAVE_
src/spectral/: add const qualifiers
src/spectral/phasevoc.c: use ishift for perfect reconstruction with odd length window
src/spectral, src/onset, src/tempo: make sure win_size > 1
src/spectral/phasevoc.c: improve error messages
src/spectral/phasevoc.c: fix argument checks
src/spectral/phasevoc.c: avoid unsigned < 0 comparison
src/spectral/phasevoc.c: compute start, end, scale, and memory sizes only once
src/spectral/phasevoc.c: improve, accept that hop_s == buf_s
src/spectral/phasevoc.c: optimize swapbuffers by using memcpy
src/spectral/phasevoc.c: check win_s and hop_s
src/spectral/phasevoc.c: indent