Created ValueStateSet class to manage the creation of multiple states by a method.

Created ValueStateSet class to manage the creation of multiple states by a method.
Modified the new EvalBinOpNN to generate states instead of nodes.  This is a much simpler interface and is what clients will want to do.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@53750 91177308-0d34-0410-b5e6-96231b3b80d8