Working but for now inactive code to support non-solvables (things which

Working but for now inactive code to support non-solvables (things which
have attributes, but are not solvables).  The usual functions interpret
negative entry numbers as those (positive ones are solvable IDs).  I'll
probably refine the code some more, hence it's work in progress.

susetags2repo: Parse also a "=Lan:" tag, which can be injected
externally when multiple language tag files are catted together.