swift234

Conformance lookup table: delay parsed extensions when we have no resolver.

If we try to visit a parsed extension (to find its protocol
conformances) when we don't have a resolver, we would get no
information out of the extension and never revisit it. Queue up these
extensions to be processed later, when we do have a resolver.

I’ve only ever seen this happen when building the standard library,
where verifying imported modules after checking a source file can
cause otherwise-unused extensions to get skipped, although they would
be needed later. The following commit depends on this, but this issue
is separable.

Swift SVN r27945