two different modules. Not sure who might be using this, so
it seems unwise to actually fix this problem.
Also document the fact that calling this function is unlikely
to be useful unless you know the package is already installed.
closes PR 12719
- fixed planet to actually use the uninstalled (.plt file) cache
- linkage code was completely broken, so it now stubbed out (see the file to
resurrect it)
- other minor cleanups
