MFC r202150, r202170:
Make OSS_GETVERSION ioctl really work. It has 'M' group, not 'P',
as different nearby ones, and was grabbed by MIXER_xxx() handler.

While there, replace '(cmd & MIXER_xxx(0)) == MIXER_xxx(0)' expressions
with more correct '(cmd & ~0xff) == MIXER_xxx(0)'. Use of bit operations
to compare numeric fields doesn't looks sane.