Revert "[ptr-traits] Implement the base pointer traits using the actual"

The commit we revert is rather small, but it enables a larger piece of new
infrastructure that allows to detected misuses of pointer-traits at compile
time. Unfortunately, this change breaks with the use of incomplete types (e.g.
in Polly). As I am not aware of a simple fix on the Polly side, I temporarely
revert this commit to clean the bots and sync-up with Chandler how to best
adapt to these recent changes.

This reverts commit https://llvm.org/svn/llvm-project/llvm/trunk@256620.

llvm-svn: 256642