Two changes:

(1) Moved the SValuator object from GRExprEngine to ValueManager.  This
   allows ValueManager to use the SValuator when creating SVals.

(2) Added ValueManager::makeArrayIndex() and
    ValueManager::convertToArrayIndex(), two SVal creation methods
    that will help RegionStoreManager always have a consistent set of
    SVals with the same integer size and type when reasoning about
    array indices.

llvm-svn: 75882