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

Closes #169

Add a new CommandResult code called "FINISH" which, unlike "CLOSE",
will attempt to flush the output buffer.  This is a one-shot attempt;
it will do one write, and not try again.

This lives in protocol/result.h now.

Eliminate the hack in handle_idle().

Just use the values assigned by the compiler.

Prepare for splitting command.c.

Remove GLib dependency from some headers.

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.

We want to remove gcc.h eventually. This takes care of all the G_GNUC_PRINTF
macros.

"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.

Replace a custom data structure with a GLib one.

Instead of returning 0 for success and -1 for failure, return true or
false.  This seems more natural.

Also add names for "error" and "ok".  I don't like passing anonymous
integer codes around.

This is not yet complete: lots of functions (e.g. in playlist.c)
follow the same convention of -1/0, and these have to be adapted, too.

Eliminate CamelCase in all public and static functions.

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

Don't pass a pointer to client->permission to processCommand(), better
let the code in command.c use the new permission getter/setter
functions.

commandError() has been superseded by command_error(), and is not
being used anymore.  Remove it.

These two functions take a client struct instead of the file
descriptor.  We will now begin passing the client struct around
instead of a raw file descriptor (which needed a linear lookup in the
client list to be useful).

As usual, include only headers which are really needed.

Instead of passing the pointer to the "expired" flag to
processListOfCommands(), this function should use the client API to
check this flag.  We can now remove the "global_expired" hack
introduced recently.

Start exporting the client struct as an opaque struct.  For now, pass
it only to processCommand() and processListOfCommands(), and provide a
function to extract the socket handle.  Later, we will propagate the
pointer to all command implementations, and of course to
client_print() etc.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7346 09075e82-0dd4-0310-85a5-a0d7c8717e4f