This reduces duplicates in the music database by hiding the original
song file when it is referenced by a CUE sheet.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1275

Don't allocate any memory until the output is really enabled.

The implementation was removed 12 years ago in commit f6455d5f and
nobody missed it.

This reverts commit 9200fa6d.  It was
wrong because it works only if the target song has already been
scanned.

Allows win32_main() to throw exceptions.

These malformed strings must not be transferred over the wire, because
the MPD protocol is defined to be UTF-8.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1274

The wrong variable was used.  This has been broken by commit
4eeea640 seven years ago - and nobody as noticed, d'oh!

libavahi-client uses this one to schedule events immediately.
However, CoarseTimerEvent may be called too late, and cause timeouts.

Deprecated in C++17.  Since C++17, one is supposed to declare those 5
types manually.