Cross-crate calls to inherited methods don't work

[catamorphism]

If you rewrite the test case from #3979 to have the traits in a different crate from the impl, trans will ICE. I'm about to check in an xfailed test case (as part of the pull request that fixes #3979).

[catamorphism]

(at least in default methods, anyway)

[catamorphism]

Not critical for 0.6; de-milestoning

[catamorphism]

Nominating for milestone 5, production-ready

[pnkfelix]

Blocks #2794 (referencing here so that it shows up, with a status, on the #2794 page).

[msullivan]

OK, this seems to work just fine, once I fix the test case. I think the problem was just that crosscrate default methods didn't work at all, which I fixed a while ago. Closing.