hack AudioAnalyzer for VAMP Onsetdetect

hack AudioAnalyzer for VAMP Onsetdetect

This works around a bug in OnsetDetector.
It requests a buffer of 1114 samples but later FFT
bails out if the buffer size is not a power-of-two.
Also large buffersizes fail.

Work-around: use ADAPT_ALL_SAFE (no buffersize
adapter), use a reasonably small buffersize.
The current settings work, even though it produces
the following warnings (vamp-plugins/OnsetDetect.cpp)

WARNING: OnsetDetector::initialise: Possibly sub-optimal step size for this sample rate: 512 (wanted 557)
WARNING: OnsetDetector::initialise: Possibly sub-optimal block size for this sample rate: 1024 (wanted 1114)

This commit should be reverted once VAMP/QM/aubio
is updated/fixed.