Re-enable verification of test and update outdated diag checks

Going by PR6913 it looks like this one can no longer reach CodeGen so remove
the redundant -emit-llvm case and treat it as an ordinary Sema test.
Fix three tests that weren't checking anything

Add -verify and update the test directives to match current expectations.

Also add a FIXME to an ObjC test that has expected-* directives but no -verify.