Fixes false negatives:

 http://foo/dav/example.ogg mismatches http://foo/dav/

.. because StringAfterPrefix() returns just "example.ogg", without
trailing slash (it existed, but was eaten already by the base
matcher).

Fixes a GCC warning because %llu appears to be unsupported by the
Windows standard library.

release v0.20.5

Allow multiple arguments.

Some missing bits when converted to C++ exceptions...

Preparing the protocol spec for multi-player support.

Fixes a potential deadlock introduced by commit 94528735

Using variable-size objects is not worth the trouble here.  Let's drop
this and use existing and simpler code.

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??

With this commit, multi-player support becomes possible... it's just
not wired to the frontend yet.

This is based on massive amounts of refactoring work I did over the
past 9 years.

The first step to multi-player support.  Not much, just a dummy
command.