Infelicities surrounding SAW's support for PtrTo in LLVM

[RyanGlScott]

If you want to construct and LLVMType representing a pointer (i.e., llvm-pretty's PtrTo), then you're going to hit one of the following difficulties:

• The Python bindings have a ptr function, but in practice, it's broken. The SAW remote API dictates that the field accompanying the pointer tag be named to type, but the Python bindings use a field named points to.
• SAWScript doesn't have an equivalent to ptr at all. The closest thing it has is the llvm_type function (e.g., llvm_type "i64*"), but we should have a separate llvm_pointer : LLVMType -> LLVMType function for constructing PtrTos directly.

It should be relatively straightforward to solve both of these, so I'll optimistically assign myself.