Don't pass a static buffer to map_spl_utf8_to_fs().

If no music_directory is configured, fall back to the XDG music
directory, determined by
g_get_user_special_dir(G_USER_DIRECTORY_MUSIC).

Nobody is using the signal_check library anymore.

This patch also removes the SIGUSR1 handler.

The signal_check library went out of order when we started using the
GLib main loop.  Convert the SIGHUP handler to use event_pipe instead.

event_pipe_emit_fast() is aimed for use in signal handlers: it doesn't
lock the mutex, and doesn't log on error.  That makes it potentially
lossy, but for its intended use, that does not matter.

There is no reason to use the shortcut "mix" instead of "mixer".

Don't start the daemon when MPD is called with "--version".

Make the event_pipe (formerly main_notify) send/receive a set of
events, with a callback for each one.

The default event PIPE_EVENT_SIGNAL does not have a callback.  It
is still there for waking up the main thread, when it is waiting for
the player thread.

Continuing the previous patch.

We are going to migrate away from the concept of notifying the main
thread.  There should be events sent to it instead.  This patch starts
a series to implement that.

Removed all macros which are already provided by GLib.

Use GLib's G_GNUC_UNUSED instead of gcc.h's mpd_unused.

Use GLib's G_GNUC_UNUSED instead of gcc.h's mpd_unused.

Use GLib's G_GNUC_UNUSED instead of macros from gcc.h.

With the GLib main loop, the client manager can install its own event
in case a client is expired.  No need for main.c to call
client_manager_expire() manually.

These functions are not used anymore since we use the GLib main loop.

Remove the event source from the GMainLoop object in
client_set_expired().

We don't need to use asynchronous events to quit MPD, we can just call
g_main_loop_quit() inside the handler.

Other libraries may need to access the main_loop reference, to add or
remove events, or to call g_main_loop_quit().

We have no child processes anymore.  Remove the SIGCHLD handler.

The SIGHUP handler was used by the update process to make the main
process re-read the database.  We don't need this anymore, since the
update takes place in a thread now.

Most of these functions were obsoleted when we switched to threaded
MPD.

This is a rather huge patch, which unfortunately cannot be splitted.

Instead of using our custom ioops.h library, convert everything to use
the GLib main loop.

Currently, both sides of the pipe are blocking, although we do not
need blocking read().  Convert it back to blocking.  Eliminate the
select() from wait_main_task().

To wake up the main thread, don't attempt to use a GCond/GMutex
(struct notify).  This kind of mixed wakeup method has known race
conditions.

The idea behind this patch is: for wakeups which happen while the main
thread is sleeping, use only a pipe.  For wakeups which happen while
the main thread is waiting for the player thread, we can later change
to GCond.  For now, accept the overhead of using a pipe for the
latter.

In the long run, the main thread will never wait for the player
thread, but will do everything asynchronously.

There is no point in making the server socket non-blocking.  We call
accept() only after select() has notified us about a new connection.

The new WIN32 version of set_nonblocking() can only deal with sockets,
i.e. it will fail on main_notify.c.  On WIN32, we have to reimplement
main_notify.c anyway, so this is not a big deal.

There are no unix sockets on WIN32, and therefore no authentication.
WIN32 might have similar capabilities, but until we implement them,
disable that MPD feature.

Sleep() has only millisecond granularity, but good enough for now.

On Windows, socket declarations reside in winsock.h and ws2tcpip.h.
The POSIX headers are not available.

Add G_GNUC_UNUSED attributes.

To test if a string is empty, we can just see if the first byte is 0.
No need to include string.h for strlen() here.

Moved implementation specific code to their own sources, internal
declarations in zeroconf-internal.h.

If the configured avahi service name is invalid, abort MPD.  Don't
fall back to the default service name.

srandom() and random() are not portable.  Use GLib's implementation.

Don't bother to call fstat() or isatty() on STDIN_FILENO.

redirect_stdin() is a daemonization function, and disconnecting from
the standard input is always a good idea for MPD.