TODO.z81

osssound_frame() somehow manages to take (on my machine) 30% CPU,
despite apparently never needing to do more than a single blocking
write(). I've never quite figured out what exactly is up with that.
The sample rate doesn't affect it, and replacing the write() with an
equivalent usleep() stops it, which seems to suggest that it's either
some weird interaction with cache, or an equally weird kernel problem.

Still, if it can be reproduced on other machines (anyone fancy trying
that? just leaving e.g. `time xz81 -a z aydemo.p' going for 30 seconds
or so would be a good enough test) it would certainly count as a bug,
and if I can't avoid it I should at least document it in the man page.


Make SCALE a command-line option rather than a compile-time one.


Add support for further AY-based sound addons, if any. The QS and Zon
were easily the most important ones, so this isn't that important
really.