Handle namespaces in a more generic way in resolve::resolve_single_import

[catamorphism]

as per FIXME (formerly XXX)

[emberian]

Still relevant

[catamorphism]

I'm going to vote for not making this change, actually; it seems like premature abstraction. I'll remove the FIXME and check in later today, but if anyone has a strong opinion, they can register it in the meantime.

[emberian]

I looked at it, and it didn't seem like there was a clean or easy way to make the change.