Abstract out everything having to do with member pointers into the ABI
class;  they should just be completely opaque throughout IR gen now,
although I haven't really audited that.

Fix a bug apparently inherited from gcc-4.2 where we failed to null-check
member data pointers when performing derived-to-base or base-to-derived
conversions on them.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@111789 91177308-0d34-0410-b5e6-96231b3b80d8
11 files changed