add mixer::loadChannel and mixer::freeChannel methods
add chan init to mixer::loadChannel
update changelog
checkout of kernelAudio and gd_config in experimental branch
update version string to 0.6.1
port kernel mixer from old MAX_NUM_CHAN to dynamic vector 'channels'
initial multichannel support, GUI+CORE only
add new methods keyboard::deleteChannel and keyboard::freeChannel
waveTools and waveform hold a *channel pointer
add style to keyboard::scrollbar
add double column channels
fix main fl_scroller size