RoarAudio's sndio emulation has been a source for annoyances.  First,
their headers turned out to be broken with C++, due to their use of
the "new" keyword.  Then they used a preprocessor macro to rename
"sio_hdl" to something else, effectively disallowing the use of
forward declarations.  Enough is enough, and I'm removing support for
it.

RoarAudio users should better use the RoarAudio output plugin.

ffmpeg plugin: when decoded stream duration is unavailable, attempt fallback to container duration (fix MusicPlayerDaemon/MPD#110)

no change in behaviour.

It does not do much harm - but it causes an unnecessary (failing)
system call.

It was implicitly deleted since commit
db23c2f2

Needed for WStringView.