Change audiobuffers sizes for tolerable latency
split off ui and MIDIeventhandler

And remove DOS compatibility.
split off seqplay

alsa sequencer in separate file
Revert "Change audiobuffers sizes for tolerable latency"

This reverts commit b331089440c7b4c850e77944f0bd20f41df52f8a.
Not needed in midiplay.cc, just in seqplay.cc.
remove unused midi playing code from seqplay