#468 support for OSSv4

[IOhannes m zmölnig]

one of Pd's older audio-backends is OSS.
while OSS is rather old and not a fast-moving target, some development does happen...
e.g. a while ago (probably years) all SOUND_PCM_-defines have been renamed to SNDCTL_DSP_.
luckily, the linux headers provided fallback defines, so old code (like Pd) would still compile.

now OSS is not dead and is currently developed as OSSv4.
unfortunately, the new OSSv4 headers have dropped the old fallback defines, and instead pro-actively create errors when the old defines are still used.

the attached patch changes these defines (and provides fallbacks in case the *new* defines are not defined), in order to be able to still use the OSS backend.

[IOhannes m zmölnig]

apply with "git am <filename>"

[IOhannes m zmölnig]

raising priority since the old s_audio_oss.c breaks compilation.

[Miller Puckette]

applied to 0.44