Enhances SCA to process untyped region to typed region conversion.

Enhances SCA to process untyped region to typed region conversion.
 - RegionView and RegionViewMap is introduced to assist back-mapping from
   super region to subregions.
 - GDM is used to carry RegionView information.
 - AnonTypedRegion is added to represent a typed region introduced by pointer
   casting. Later AnonTypedRegion can be used in other similar cases, e.g.,
   malloc()'ed region.
 - The specific conversion is delegated to store manager.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@59382 91177308-0d34-0410-b5e6-96231b3b80d8