swift234

Teach TypeChecker::resolveTypeInContext to use interface types more often.

When referring to a type declaration that is a member of some nominal
type, we were relying on substitution into the non-interface type,
which is silly. Use the interface type here.

Other than some type-printing differences, this should be NFC.

Slight regression in two compiler crashes that had been fixed in the
previous commit; I'll look into these shortly.

Swift SVN r25385