Log Message:
portaudio: In the OSS hostapi, support additional sample formats.

While here, adjust some hacks around differences between NetBSD ossaudio
and OSSv4:

It turns out the problem was Audacity attempting to initialize with
an absurdly high sample rate. When a sample rate that's outside the
range of the kernel's maximum of 192000 is passed to SNDCTL_DSP_SPEED,
-1 was returned (until my commits today).

This is a violation of the OSSv4 spec in NetBSD. The spec states that if
an unsupported sample rate is requested, a supported one should be picked
and returned.