This adds parsing of the qualifiers ptr32, ptr64, sptr, and uptr and
lowers them to the corresponding address space pointer for 32-bit and 64-bit pointers.
(32/64-bit pointers added in https://reviews.llvm.org/D69639)
A large part of this patch is making these pointers ignore the address space
when doing things like overloading and casting.
Can this be simplified to:
Mainly I wanted to avoid recomputing isPtrSizeAddressSpace for A and B.
I think it's only not equivalent when A and B are both default, but we already return true in that case.