Simplify the definition of many build options.

Make sure glibc gives us all features.

Remove the runtime check for eventfd(), hard-code the feature once
it's been selected at compile time.  The class WakeFD is splitted into
EventFD and EventPipe, using WakeFD as a macro diversion.

Wrap close(), use closesocket() on WIN32/WinSock.

Don't provide the prototype if inotify_init() was not detected.

Unfortunately, there's no "optimized" implementation here.  We can't
use Linux's proprietary system call dup3(), because it would require
us to specify the new descriptor.

Add a "mode" argument to open_cloexec() instead.

Same as pipe_cloexec_nonblock(), but doesn't set non-blocking mode.

We'll copy this code to libmpdclient, and that's easier if its license
is BSD.

Changed the wrappers for pipe(), socket(), accept().  On WIN32, this
does not work for pipe().

This function is used only internally.

Added wrapper for inotify_init1() to fd_util.c.

Added the "fd_util" library, which attempts to use the new thread-safe
Linux system calls pipe2(), accept4() and the options O_CLOEXEC,
SOCK_CLOEXEC.  Without these, it falls back to FD_CLOEXEC, which is
not thread safe.

This is particularly important for the "pipe" output plugin (and
others, such as JACK/PulseAudio), because we were heavily leaking file
descriptors to child processes.

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.

Added a small RIFF parser library.  Look for an "id3" chunk, and let
libid3tag parse it.

Moved everything related to saving or loading the playlist from/to the
state file to playlist_state.c.

In generic PCM functions allowing all sample formats, pass a void
pointer instead of a char pointer.

Moved the software mixing code (used by crossfading) to a separate
library.

Don't use libc's rand() function, because it is slow.  Our own trivial
linear congruential generator is good enough for dithering.

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