swift234

IRGen: Test emission of conformances for concrete subclasses of generic classes

This was fixed by Luke Howard as part of some other changes in the
following patch:

<https://github.com/apple/swift/commit/b5880f386b814f8b5cb220d1c4e65e74c04eccf4>

After rebasing my fix, I noticed most of it disappeared.
However, it's still worth checking in the tests.

Fixes <rdar://problem/24183374>.