Only _WIN32 is defined by the compiler, and WIN32 is not standardized
and may be missing.

Closes #169

This reverts commit f0be48ff
(except for the NEWS entry).

If libdispatch (GCD) is used before forking, it
can't safely be used again after forking.

Add class Context which wraps the Android/Java Context class and add a
JNI wrapper for method Context.getCacheDir().

Replaces global variable "main_loop".

More preparations for multi-player support.

The main_cond variable was completely unnecessary.  The pc.cond object
can be used for both main->pc and pc->main.

This is the beginning of multi-player support.  There will be support
for multiple Partition objects in one MPD process.

Allocate a player_control object where needed, and pass it around.
Each "client" object is associated with a "player_control" instance.

This prepares multi-player support.

I've added PIPE_EVENT_SHUTDOWN because calling g_main_loop_quit() do not work when called from another thread.
Main thread was sleeping in g_poll() so I needed some way to wake it up.

By some strange reason call close(event_pipe[0]) in event_pipe_deinit() hangs.
In current implementation that code never reached so that was not a problem :-)
I've added a conditional to leave event_pipe[0] open on Win32.

Use GMutex/GCond instead of the notify library.  Manually lock the
player_control object before accessing the protected attributes.  Use
the GCond object to notify the player thread and the main thread.

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.

There is only one location using PIPE_EVENT_SIGNAL: to synchronize
player_command() with player_command_finished().  Use the "notify"
library instead of the event_pipe here.

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

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

Prepare for the migration to the GLib option parser, which uses
gboolean for flags.

"LOG_H" is a macro which is also used by ffmpeg/log.h.  This is
ffmpeg's fault, because short macros should be reserved for
applications, but since it's always a good idea to choose prefixed
macro names, even for applications, we are going to do that in MPD.

When there are standardized headers, use these instead of the bloated
os_compat.h.

Similar to decoder_control.c, output_control.c will provide functions
for controlling the output thread (which will be implemented later).

This function is declared, but is neither used nor implemented.