Simplify the definition of many build options.

I've created an elementary input plugin that plays sound from the
soundcard, so you can use MPD to listen to anything connected to the
line-in jack, or to Video4Linux FM radio cards that send audio through
the soundcard.  There has been a small number of posts here in the
past requesting line-in input, so here is a first, simplistic stab at
it.

The patch adds a new sheme, alsa://, which causes mpd to play data
read directly from a souncdard.  It defaults to hw:0,0, but you can
pass any ALSA device name in the URI.  So, using mpc for example:

 mpc add alsa://
 mpc play

will play from device hw:0,0.

To use a diffferent device:

 mpc add alsa://hw:1,0

Replaces GLib's g_str_has_prefix().

This plugin is cumbersome to support, now that MPD is migrating away
from GLib and the GLib event loop.  It has no practical advantages
over the CURL plugin.  Soup requires the bloated GType library.

Remove GLib dependency from some headers.

To demonstrate the new I/O thread.  libsoup is well-integrated into
the GLib main loop, which made this plugin pretty easy to write.

As a side effect, we have to initialize the I/O thread in all debug
programs that use the input API.

For Spotify tracks. Uses a spt URI, so with mpc you can play tracks
with e.g.,

  mpc add spt://spotify:track:5qENVY0YEdZ7fiuOax70x1
  mpc play

Uses the pcm_decoder_plugin for the output

After we've been hit by Large File Support problems several times in
the past week (which only occur on 32 bit platforms, which I don't
have), this is yet another attempt to fix the issue.

This has been replaced by the last.fm playlist plugin.  The input
plugin has never worked well, and was just a playground to experiment
with the last.fm radio protocol.

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.

Since there are no other callers than stdout, this wouldn't be a
problem, but since there maybe in the future go ahead and fix it.

The lastfm input plugin enables MPD to play lastfm:// URLs.  This
plugin is not complete yet: it plays only the first song in the
last.fm playlist, and the playlist parser isn't even implemented
properly.

"ls" is a bad name for a library which parses URIs.  We'll move the
rest of the "ls" library later.

This patch implements the MMS protocol, by using libmms.  It is quite
experimental: it does not support seeking yet, and it is currently
using synchronous I/O, which causes MPD to hang while waiting for the
server.