Move code from the "vorbis" decoder.

libsmbclient is not thread-safe nor reentrant.  We must protect all
function calls with a global mutex, unfortunately.

This appears to be the right thing to do when we want anonymous login.

After we've been hit by Large File Support problems several times in
the past week (which only occur on 32 bit platforms, which I don't
have), this is yet another attempt to fix the issue.

The soure file client.c has nearly 1000 lines, time for splitting it
into smaller pieces to improve readability.

Prepare splitting client.c into several sources.

Make the client list management a separate sub-library.

The client code uses portable GLib I/O functions and doesn't need the
OS specific socket headers.

Several functions work with the wrong return type, this patch fixes
them.

When client_defer_output() aborts the connection to the client,
client_write_output() called client_write_deferred() anyway.  This
caused an assertion failure.  Fix it by checking for the "expired"
flag again after client_defer_output() returns.

I'm hunting down a bug where client->channel==NULL during I/O
operations.  These new assertions help avoid this kind of bug in the
future.

This patch fixes a memory leak: the fifo_buffer object was not freed
when the client connection was closed.

On both locations, the result of write() can be ignored safely.  In
event_pipe_emit_fast(), that can only be "EAGAIN", which means that
the pipe buffer is full - no further notification required.  In
client_init(), that would be a fatal connection error, which would be
caught by the next event.

This patch fixes gcc warnings.

This updates the copyright header to all be the same, which is
pretty much an update of where to mail request for a copy of the GPL
and the years of the MPD project. This also puts all committers under
'The Music Player Project' umbrella. These entries should go
individually in the AUTHORS file, for consistancy.

Removed the sockaddr_to_tmp_string() hack, use
the new function sockaddr_to_string() instead.

Since we introduced a GLib logging domain, the "client" string appears
twice in the log lines:

 client: client 0: command returned 0

Removed the second one, now it looks like this:

 client: [0] command returned 0

Still not quite good, but better than before.

When we do not explicitly catch G_IO_ERR and G_IO_HUP, GLib can go
into an infinite loop, because it won't deliver the socket error to
MPD.