Remove use of comma operator.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209871 91177308-0d34-0410-b5e6-96231b3b80d8
Add a trivial ArrayRef helper overload to the SelectionDAG interface.
I'm using this pretty frequently in a patch I'm working on and it seems
generally useful.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209872 91177308-0d34-0410-b5e6-96231b3b80d8