sysutils: add apt-mirror (devel version)

A small and efficient tool that lets you mirror a part of or
the whole Debian GNU/Linux distribution or any other apt sources.

Main features:

• It uses a config similar to APT's F<sources.list>
• It's fully pool compliant
• It supports multithreaded downloading
• It supports multiple architectures at the same time
• It can automatically remove unneeded files
• It works well on an overloaded Internet connection
• It never produces an inconsistent mirror including while mirroring
• It works on all POSIX compliant systems with Perl and wget