Bump up default RTP player buffer sizes. Now big enough to keep ALSA

Bump up default RTP player buffer sizes.  Now big enough to keep ALSA
(first doubling) and ALSA's OSS emulation (second doubling) fed.  The
initial buffer size is still under half a second, and feels close to
instant to this listener.

Also, the player thread now consumes packets immediately rather than
waiting for the next iteration, preventing a race where the (inner)
playing loop at the bottom of main() can terminate unnecessarily
early.

There's bits of debugging code left lying around commented out.  It's
harmless for now!