Decent Notation and MIDI `piano roll' editor

MIDI: Rosegarden development is focused on ALSA. This release can use
MIDI on non-ALSA systems, via aRts; sequencer playback, recording, and
step-recording in the notation and matrix editors are all usable, with
these caveats: (1) the OSS support in aRts uses only the raw MIDI nodes,
not the in-kernel sequencer, so its timing precision is limited by
scheduling of the artsd user process, and involves frequent IPC among 3
user processes; the surprise is it works at all, but on a lightly loaded
system it is listenable. (2) at present only one playback client gets
registered with the aRts MIDI manager, limiting playback to 16 MIDI
channels. (3) the matrix and notation editors give audible feedback of
chosen notes over MIDI output, but Note Off is not sent; be sure to choose
a patch without sustain for the echo voice.

Audio: the developers support ALSA and JACK. There is aRts audio code
in this release and it compiles, but I have tested nothing.

Note that this release of rosegarden is not considered to be fully stable.
