Move away from the poor "abstraction" I added to Type. John argued

Move away from the poor "abstraction" I added to Type. John argued
effectively that this abstraction simply doesn't exist. That is
highlighted by the fact that by using it we were papering over a more
serious error in this warning: the fact that we warned for *invalid*
constructs involving member pointers and block pointers.

I've fixed the obvious issues with the warning here, but this is
confirming an original suspicion that this warning's implementation is
flawed. I'm looking into how we can implement this more reasonably. WIP
on that front.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@133425 91177308-0d34-0410-b5e6-96231b3b80d8