As typed pointers are no longer supported, we should no longer
specify element types in intrinsic signatures.
The only meaningful pointer types are now:
llvm_ptr_ty -> ptr
llvm_anyptr_ty -> ptr addrspace(any)
LLVMQualPointerType<N> -> ptr addrspace(N)
This is only "partially" because we also have a bunch of special
IIT descriptors like LLVMPointerTo, LLVMPointerToElt and
LLVMAnyPointerToElt, which I'll leave for a later revision.
Differential Revision: https://reviews.llvm.org/D155086