memcached: import from packages, add myself as the maintainer

This adds the memcached package from the old svn package fee. I adopt
the licensing information an will maintain the package in the future.
This request also updates memcached to the last stable version 1.4.20.
Building was testet with target x86_64, ar71xx and avr32

Signed-off-by: Thomas Heil <heil@terminal-consulting.de>