Mention libao-alsa
Fix libao-alsa.
Restrict the explicit -lgcc_s to Linux as the comment indicates where it
is aimed at.
Put binaries back into the directory the PLIST expect them in.
Needs pkg-config.
Newer NetBSD has shm_open, use a common PLIST fragment for all systems
using it.
Mark as not ready for python-3.x.