Some minor style fixes as well.

This can happen if you remove an external audio card or if you stop
sndiod(8) while playing a song.

sio_write() will retry internally if it fails with errno == EINTR
so no need to handle that.

It defaults to 250 ms.

Fixes build failure on Debian Wheezy.

Use the snd_pcm_t only in the IOThread, and reuse code that is
well-known to work.

Comes with a callback pointer instead of a virtual method, which
allows multiple instances in one class.

Replaces the old BoundMethod template.

release v0.19.16

Previously the id was being returned only when a position wasn't
specified.

.. instead of doing it after seeking.  After seeking, the command had
no effect, because CheckDecoderStartup() waits for all outputs to
finish.  This caused a very long delay while seeking and switching
songs (https://bugs.musicpd.org/view.php?id=4534).

Signed-off-by: Lazaros Koromilas <lostd@2f30.org>