In lookupTopBndrRn, if we're in an interface file, then create the
binder in the cache with the correct Module (inc. package name) rather
than making a vanilla module as we do currently.

This helps to get the package names right in names from interfaces
that we've read via checkOldIface (ie. "skipped" modules), and fixes a
bug to do with unnecessary version bumping and recompilation.

(Simon P.J. will add a better comment later)

MERGE TO STABLE