Version numbers

A version number consists of two parts: the upstream
version, and the debian revision, which are seperated
by a hyphen (-). Each part may consist of alphanumeric
ASCII characters and the characters `.', `+', `-' and
`:'. If there is no debian revision then the upstream
version is not allowed to have a -.

Comparing version number is done by breaking them into
pieces and comparing those from left to right. Pieces
are seperated by a transition from numbers to
characters and by non-alphanumeric characters.