remove cruft
Fix crash when instrument plugins fail to instantiate.
towards a SRC source + resampling during audition
mark session dirty when panner-bypass is toggled
add meter-peak (display&reset) button to gain-meters by default
fix typo in VST flags
fix XML parser error:

XML declaration allowed only at the start of the document
audition: resampler use same quality as import
visibility macros and flush() added to SrcFileSource; merge with master