Fixes hanging playback with soxr resampler.

Closes #139, #141

Tremor decoder is unusable since commit 2ee43c40. Sound is distorted to
the point where it's nothing but noise.

The data from vorbis_synthesis_pcmout() needs to be scaled and
clipped for 16 bit sample size. For reference see
http://lists.xiph.org/pipermail/tremor/2010-April/001642.html and
http://lists.xiph.org/pipermail/vorbis/2006-October/026513.html.
Signed-off-by: Marcin Jurkowski <marcin1j@gmail.com>

Fixes the non-Linux build.

This loop was introduced in commit
24c1f463, but -EPIPE is not a possible
error condition for snd_pcm_hw_params().  This code does not appear to
make sense.  Problems with a wrong period_time should be caught before
that by snd_pcm_hw_params_set_period_time_near().

This commit removes the last "goto" in MPD!  Yay!

It's not possible to set CURL options after curl_easy_perform(), and
thus the CURLOPT_RANGE had no effect.

From the CURLOPT_RANGE documentation: "The application does not have
to keep the string around after setting this option."

Apparently, connecting a socket to a loopback address can block on
Windows, and a non-blocking socket will return WSAEINPROGRESS.  This
broken PoorSocketPair() in commit 2119e4fd, which made the socket
non-blocking right from the start.  This fix postpones the
ioctlsocket(FIONBIO) call until after the connect().

Closes #134

release v0.20.11

Turns out that using CP_ACP is a lousy idea, because only very few
Unicode characters can be represented by it.  Instead, switch to UTF-8
(which every sane person on other operating system already uses).

Closes #102

Applies the improvements from the previous commit to the "seek"
commands, which are also capable of switching songs.

Closes #119

Our previous use of Queue::SwapOrders() could cause surprising
results:

- sometimes, the old "current" song would be played again (if the
  newly selected song had not been played already)

- sometimes, the old "current" song would not be played again (if the
  newly selected song had already been played)

This is inconsistent, because it should not depend on whether the
newly selected song had already been played.

So instead of Queue::SwapOrders() we now use Queue::MoveOrderAfter()
and Queue::MoveOrderBefore(), which is more expensive, but also more
consistent.  It attempts to retain as much from the previous order
list as possible, and only moves the newly selected song around.

If an early exception gets caught (e.g. from
AllocatedPath::FromUTF8Throw()) before
DecoderControl::CommandFinishedLocked() is called, the decoder thread
would go in an endless loop, because DecoderCommand::START is still
set.

Closes #118

GME starts all track indexes at zero, but subtune prefixes
start at one. This fixes an off-by-one error during track
enumeration.

GME starts all track indexes at zero, but subtune prefixes
start at one. This fixes an off-by-one error during track
enumeration.