Fix ARM HVA classification of classes with non-virtual bases

Reuse the PPC64 HVA detection algorithm for ARM and AArch64. This is a
nice code deduplication, since they are roughly identical. A few virtual
method extension points are needed to understand how big an HVA can be
and what element types it can have for a given architecture.

Also make the record expansion code work in the presence of non-virtual
bases.

Reviewed By: uweigand, asl

Differential Revision: http://reviews.llvm.org/D6045

llvm-svn: 220972