swift234

[SR-427][AST] Report DoesNotConform for failed substitutions in a bound generic type.

If a BoundGenericType is unable to get a substitution for an archetype
it uses ErrorType as the replacement (Module.cpp:705). In such a case
we should report DoesNotConform in lookupConformance(), which ends up
generating reasonable error messages. Prior to this change the
conformance would succeed and then IRGen would crash on emitting an
ErrorType during emitForeignTypeMetadataRef().

Also added test that tickles crash near the same place as SR-427.