[Verifier] Verify invokes of intrinsics

We support invoking a subset of llvm's intrinsics, but the verifier didn't account for this.  We had previously added a special case to verify invokes of statepoints.  By generalizing the code in terms of CallSite, we can verify invokes of other intrinsics as well.  Interestingly, this found one test case which was invalid.

Note: I'm deliberately leaving the naming change from CI to CS to a follow up change.  That will happen shortly, I just wanted to reduce the diff to make it clear what was happening with this one.

Differential Revision: http://reviews.llvm.org/D10118

llvm-svn: 240836