Allow vectors in CreatePointerCast.

Both underlying IR operations support vectors of pointers already.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172538 91177308-0d34-0410-b5e6-96231b3b80d8
[msan] Fix handling of equality comparison of pointer vectors.

Also improve test coveration of the handling of relational comparisons.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172539 91177308-0d34-0410-b5e6-96231b3b80d8