Events in the delay-buffer must be shifted back every cycle.
Also in case of fixed-delay-lines events may not be in sequence
since events are only sorted at backend port-level.
MidiBuffer::read_from() clears the buffer, so events were not
accumulated into the delay-buffer.
This also includes a small optimization and comments for the
variable delayline.
Generated by tools/f2s. Some hand-editing will be required in a few places to fix up comments related to timecode
and video in order to keep the legible
