After conversations with Zhongxing Xu and Jordy Rose, refine the logic in

RegionStoreManager::RetrieveElement() that handles indexing into a larger scalar
object to only consult the direct binding of a super region if it is a scalar.
This isn't perfect yet, and a big FIXME is attached to the code.  This causes
the test case for PR 7218 now to pass.

llvm-svn: 105195