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.

Merged freeAllListenSockets() into closeAllListenSockets(), because
this is its only caller.

Disable changeToUser(), daemonize(), killFromPidFile().

On WIN32, parsePath() now simply duplicates the input string.  There
is currently nothing special we can do here.  The old code was not
portable on WIN32.

Use g_get_home_dir() to get the home directory of the current user.
This will be portable to win32.

Declare variables where they are really used.

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

Removed the fallback setenv() implementation for solaris.

Removed GLib logging wrappers which are not used anymore.

If a log message does not include a newline character, append it.