These were two representations of, essentially, the same information.
They were separate because they provided different APIs to similar
information, but the APIs became more similar once we started using
native types (as opposed to Noms types) for the various Make*TypeRef()
functions.
Unifying these is a big step to unifying parse.Package and types.Package,
which is pretty necessary for dealing with imported packages.
Fixes issue #338
c80a1c55b3