This gets the alsa target working nicely for mmapped outout. I'm not
certain, but I think it will even deal with NPOT buffer sizes (I copied
the code from libasound's sample pcm.c, thus the uncertainty).
Non-mmapped output isn't supported yet, but the alsa target now works
nicely for pull rendering.
However, some work still needs to be done for recovery failure: either
disable the sound system, or restart the driver entirely (preferable).
This brings the alsa driver in line with the jack render (progress
towards #16), but breaks most of the other drivers (for now: one step at
a time). The idea is that once the pull model is working for at least
one other target, the jack renderer can become just another target like
it should have been in the first place (but I needed to get the pull
model working first, then forgot about it).
Correct state checking is not done yet, but testsound does produce what
seems to be fairly good sound when it starts up correctly (part of the
state checking (or lack thereof), I imagine).
1) when /not/ building static plugins, the plugin info name is, once again,
PluginInfo, but is still type_name_PluginInfo for static plugins. This
allows plugins to be symlinked (highly desirable for the debian packages,
and likely others). This also requires plugins to /not/ be loaded with
RTLD_GLOBAL.
2) because of 1, snd_alsa_0_9 has to explicitly load libasound itself. This
just happens to fix my segfault on shutdown in RedHat 6.2.
