Fixes another buffer overflow: if the stream has a very long title or
URL, resulting in a metadata string of more than 2 kB, icy_string[0]
is a negative value, which gets casted to size_t - ouch!

 https://bugs.musicpd.org/view.php?id=4652

Fixes a buffer overflow due to the bad formula rounding the buffer
size up.  At the same time, remove the "+1" from the meta_length
calculation, which takes the padding into account and at the same time
implements proper rounding.

Why did this cast exist??

Same as in commit e02d8ad8, but this time for the sndio plugin
which can be emulated by libroar.

Each close/open cycle resets the Filter's state, because a new Filter
instance is being created.  That results in the serials
(replay_gain_serial and other_replay_gain_serial) being out of sync
with the internal ReplayGainFilter state.

So instead of initializing those serials once, we need to initialize
them each time we create new ReplayGainFilter instances, i.e. in
OpenFilter().

 https://bugs.musicpd.org/view.php?id=4632

If the input AudioFormat changes but the out_audio_format doesn't
change (e.g. because there is a fixed "format" setting in this
"audio_output" section), the ConvertFilter needs to be reconfigured.
This didn't happen, resulting in awful static noise after changing
songs.

I want a compiler warning when a new state needs to be considered
here.

Fixes the dreaded error "Failed to create : No such file or
directory".

 https://bugs.musicpd.org/view.php?id=4625

We'll have some code for it soon.

Move this sample rate fixup from the ALSA output plugin to PcmExport,
where it belongs.

Prepare for DSD sample rate fixups.

Fixes assert failure after unpausing.

Reduce overhead by eliminating MultipleOutputs::ResetReopen().