It was implicitly deleted since commit
db23c2f2

Needed for WStringView.

These will be generated by the compiler automatically.

This is not necessary, because a strlen() on a literal gets optimized
away by the compiler.

Coverity discovered that the Pulse plugin could throw exceptions from
Pause(), but that method was marked "noexcept" because its caller was
not designed to catch exceptions.  So instead of avoiding exceptions
(by catching and logging them in each and every implementation), let's
allow them, and do the catch/log game in the MPD core.

The "-1" magic value is deprecated now.

Closes #107

Workaround for the following LAME build failure:

 error: inlining failed in call to always_inline '_mm_sqrt_ps': target
 specific option mismatch

This is because the LAME build scripts do not check whether SSE is
available; they only check for the presence of the "xmmintrin.h"
header.

Requiring a Pentium 3 CPU is reasonable enough, and it's the first CPU
to feature SSE support.

Fixes regression from commit 31bad5f7:
if Pause() returns true, the output thread is running a busy loop,
causing 100% CPU usage, instead of just closing the output.

Closes #105