[analyzer] Strip CXXBaseObjectRegions when devirtualizing method calls.

This was causing a crash when we tried to re-apply a base object region to
itself. It probably also caused incorrect offset calculations in RegionStore.

PR13569 / <rdar://problem/12076683>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@161710 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed