long line police
std: various hacking on workcache.
migrate gc.rs to LinearSet
migrate task/spawn.rs to LinearSet
std: Ignore time::tests::test_strptime, it's failing for some reason

I'll file an issue.
migrate coherence.rs to LinearSet
migrate gather_loans.rs to LinearSet
Merge pull request #4585 from thestinger/map

migrate LinearMap<T, ()> to LinearSet<T>
remove send_map find and get methods

These methods duplicate the find_ref and get_ref code, and aren't an
improvement over just doing the copy in the caller.

They also don't work for types that implement Clone but aren't copyable
via Copy.