Replaces GLib's GError.

playlist and player_control are deprecated.

Don't use the global variable "g_playlist".

Let the database plugin do the match.

Merge locate_song_search() and locate_song_match().

Search and add search result to a stored playlist.

Add nonnull attributes and fix all callers.

Use this struct for db_walk().

Improve error reporting and handling.  command.c gets the new function
print_error(), which sends a GError to the client.

Allow calling findAddIn() without a client object.

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.

The function is unused.

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.

Changed the function prototypes to get locate_item_list objects
instead of num_items/items.

No CamelCase and no typedefs.

Pass const pointers where no writes are performed.

Don't use dbUtils.h functions.  This reduces 4 full database walks to
just one.

"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.

Don't pass the raw file descriptor around.  This migration patch is
rather large, because all of the sources have inter dependencies - we
have to change all of them at the same time.

This patch continues the work of the previous patch: don't pass a file
descriptor at all to traverseAllIn().  Since this fd was only used to
report "directory not found" errors, we can easily move that check to
the caller.  This is a great relief, since it removes the dependency
on a client connection from a lot of enumeration functions.

The usual bunch of const pointer conversions.