Only _WIN32 is defined by the compiler, and WIN32 is not standardized
and may be missing.

Closes #169

InputStream::Read() and InputStream::Seek() are called with the mutex
locked.  That means the implementation must not block, or unlock the
mutex before calling into blocking code.

Previously, a slow CD drive could stall the whole MPD process,
including the main thread, due to this problem.

Closes #149

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."

This eliminates some overhead, because the compiler doesn't need to
consider these functions throwing.

Fixes a GCC warning because %llu appears to be unsupported by the
Windows standard library.

Fixes a GCC warning because %llu appears to be unsupported by the
Windows standard library.

Yet another potential crash bug fix.

Doesn't make a practical difference - but it's more correct this way.

Eliminate dependency on io_thread_get().

Make sure we're using the same EventLoop as the NfsManager.

Eliminate dependency on io_thread_get().

This way, we have four periods instead of the default of two.  With
only two periods, we don't get woken up often enough, and we
frequently encounter buffer overruns.  With four periods, we have more
time to breathe, and the buffer overruns magically disappear.

This setting is mostly useless for capture devices.  There's no point
in configuring it.