Improve upstream-to-package-name translation

[ThreeFx]

The Debian package naming guidelines specify that the only valid characters in package names are: [a-zA-Z0-9.+-].

The VCS hosting service sourcehut (git.sr.ht) has a tilde in front of user's names, thus confusing git-buildpackage when importing the original source.

I have no idea how the "canonical" fix for this would look. I suggest that we simply call normalizeDebianProgramName on every part of gopkg in debianNameFromGopkg (as in #128).