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.

The file systemd/mpd.service.in is being distributed implicitly, but
systemd/mpd.socket is not and needs to be added to EXTRA_DIST.

Share the NFS connection with the NFS input plugin.

Auto-stop the IO thread in all error handlers.

Read all directory entries into memory and close the struct nfsdir
before returning the StorageDirectoryReader instance.  This is what
libnfs does, anyway.

Creating a NfsStorage sets its own export_name as the "base".  Now
NfsFileReader can use this information to derive the export_name to be
mounted, instead of guessing.  This solves the "too many connection"
problem on the NFS server while updating the database.

Combines the "file" and the "archive" input plugins.

Found by "make distcheck".

Allow building a smaller MPD binary for people who don't need DSD.

The standard has been renamed since the early draft that was
implemented in MPD.

For type safety and code readability.

Reduce header dependencies.

Generate more detailed error messages.

Eliminate duplicate definition (in input plugin and decoder plugin).

This plugin uses the MP4v2 library to play mp4/m4a files.
It is limited to file_decode.

The new class is pluggable, to prepare for gzipped database files.

For now, the TextFile class remains, and will be refactored away
later.

libfs.a depends on libsystem.a.