Rationale:
- unlike current behavior this seems to be compliant with OSS
specification:
http://manuals.opensound.com/developer/SNDCTL_DSP_GETIPTR.html
- this seems to meet expectations of some OSS programs compiled for or
ported from Linux, e.g. ALSA OSS plugin
- this doesn't seem to break any programs as far as current testing
shows
Tested by: nox, hselasky
MFC after: 4 days