The way newsticker currently handles paths involves directly concating
"/", which only works for UNIX systems.

Additionally, since newsticker uses `prin1-to-string' for storing
groups and cache, it should be enforced that `print-level' and
`print-length' are set to nil for the operation just as a precaution (it
happened to me that I manually set these once, which resulted in the
newsticker cache being corrupted).

This patch should fix both of these issues.