pkg2 wip: include julia as a fixed installed "package".
pkg2 wip: provide proxy version numbers for fixed packages.

These proxy versions are necessary for making fixed packages work
properly with version requirements since one has to have a version
for each fixed package against which to evaluate the feasability of
constraints on that package's version to eliminate versions of free
pacakges that won't work with the installed fixed version.
pkg2 wip: on second thought don't let dirtiness affect proxy versions.