This is a simple, efficient way to get a recursive list of all files under
a specified directory.

It implements a typical iterator interface, making it simple to convert
code that processes a list of files to use this instead. The directory is
read as the list is consumed, so memory overhead is minimal.

This module simply loads the appropriate backend; either the
Directory::Iterator::PP manpage or the Directory::Iterator::XS manpage.
With the pure-perl backend, the speed is equivalent to the File::Find
manpage; the XS backend is a few times faster.