Add more testing cases for tbaa.struct

Testing cases for structs of structs and unions of structs.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177612 91177308-0d34-0410-b5e6-96231b3b80d8
Further weaken block conversion rules to permit blocks with
enum return type to be converted to blocks with any integer type
of the same size.

rdar://13463504

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177613 91177308-0d34-0410-b5e6-96231b3b80d8