Wildcard matches are directly applied to all filenames in
subdirectories without any attempt at matching relative paths.

This change is based on the following feature request:

  http://bugs.musicpd.org/view.php?id=3729

Replaces StatFile(), with a portable data object.

std::auto_ptr is deprecated, and std::unique_ptr is much better
anyway.

Necessary for "final" on gcc 4.6.

Eliminate support for partial reads.  The Linux kernel will never
return partial results, so this buffering was unnecessary.

Check for 0 in "device" and "inode" instead.

Remove the C list_head library and use type-safe C++ instead.

Quick hack to allow using the database without GLib (for Android).

A SimpleDatabase instance can now "mount" other Database instances at
certain locations.  This is used to use a new SimpleDatabase instance
for each storage mount (issued with the "mount" protocol command).
Each such instance has its own database file, stored in the directory
that is specified with the "cache_directory" option.

The problem with std::queue is that it doesn't give us enough control.
The method Clear() is a kludge already, but soon, we'll need
filtering.

Replaces g_strstrip().

The root WatchDirectory instance already contains the music directory,
and we don't need to fetch it again.

Replaces map_to_relative_path() from Mapper.cxx.