Add GMutex, GCond attributes which will be used by callers to
conditionally wait on the stream.

Remove the (now-useless) plugin method buffer(), wait on GCond
instead.  Lock the input_stream before each method call.  Do the same
with the playlist plugins.

Major API redesign: don't let the caller allocate the input_stream
object.  Let each input plugin allocate its own (derived/extended)
input_stream pointer.  The "data" attribute can now be removed, and
all input plugins simply cast the input_stream pointer to their own
structure (with an "struct input_stream base" as the first attribute).

Make the input_stream implementation hold a reference on the
archive_file object.  Allow the caller to "close" the archive_file
object immediately, no matter if the open_stream() method has
succeeded or not.

The archive plugin should decide this.

This fixes a NULL pointer dereference in case of archive plugin
failure.

Make archive_file a "real" struct, extended by all plugins.  Add the
plugin pointer to it.  Wrap all method calls in functions.

.. instead of manually checking pathname[0]=='/'.
g_path_is_absolute() is portable.

Fixed memory leak in error handler.

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 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.

Allow input plugins to configure with an "input" block in mpd.conf.
Also allow the user to disable a plugin completely.

Create a sub directory for input plugins.

Start to separate private from public input_stream API.

The open_stream() method opens the input_stream.  This allows the
archive plugin to do its own initialization, and it also allows it to
use input_stream.data.  We can remove input_stream.archive now, which
was unnatural to have in the first place.

This way, plugins can manipulate the plugin pointer during open().