Create Debian packages

We can now create packages on Debian systems using `dpkg-deb`.
Update to latest libcork
Remove extraneous dots in Debian versions

Debian version strings let you transition from numeric tags to alpha
tags (and vice versa) without needing an intervening dot.  So lets take
advantage of that!
Create directories with specific permissions

You must now provide a permissions mode value when creating a directory.
Before we used 0750 for everything, but the Debian control directory
needs to be 0755.