Found with readability-uppercase-literal-suffix
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with readability-const-return-type
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-redundant-void-arg
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-use-override
Signed-off-by: Rosen Penev <rosenp@gmail.com>

No output at all is fine.  If the partition needs an output, it must
be moved there, but having just a null output isn't helpful.

By eliminating GetAnyClient(), we can have instances with no outputs
at all.

Prevents compiling those sources many times, once for each debug
program using it.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/708

Apparently, Icecast defaults to ISO-8859-1 for MP3:

 http://icecast.org/docs/icecast-2.4.0/config-file.html#mountsettings

This change forces Icecast to UTF-8 without having to configure it in
Icecast's configuration file.

This is the correct thing to do for ports from which a signal ultimately
"originates", such as is the case with mpd.

This header had been available for a long time on Linux, but was
removed in glibc 2.30.  This commit moves the `#include` line inside
the `#ifdef __sun` block and adds a fake declaration of `I_FLUSH` for
the Linux build.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/630

Without this, the compiler may optimize accesses away.