Archlinux support

This adds support for Arch Linux/Arch Linux ARM. It has been around in my repo for a long time now, with a good number of users I believe, and rarely has issues.

First 3 commits are not directly related to arch, but necessary (especially the last 2).
Oh wait, saw the very sneaky ' on the line above.  Please invert it, so that the block is consistently wrapped in ', and the $package passing exits the block accordingly...