Extend ptr32 support to be applied on typedef

Earlier, if the QualType was sugared, then we would error out
as it was not a pointer type, for example,

typedef int *int_star;

int_star __ptr32 p;

Now, if ptr32 is given we apply it if the raw Canonical Type
(i.e., the desugared type) is a PointerType, instead of only
checking whether the sugared type is a pointer type.

As before, we still disallow ptr32 usage if the pointer is used
as a pointer to a member.

Differential Revision: https://reviews.llvm.org/D130123