Move the decision about the kind of CGCXXABI to make inside
the family-specific files.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173530 91177308-0d34-0410-b5e6-96231b3b80d8
ARM says that the array cookie should always be eight bytes.
ARM is not thinking about over-aligned structures.
Overrule ARM in both our generic-ARM and iOS ABI implementations.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173531 91177308-0d34-0410-b5e6-96231b3b80d8