Record if typedefs are to references as opposed to pointers

[adetaylor]

autocxx-bindgen now outputs attrtibutes to indicate whether function parameters and return types are references, as opposed to pointers.

We don't attempt to output any such attributes for typedefs. We should. The fix for #222 makes this pre-existing problem slightly worse.

Until we've done this, we'll be treating too many things as pointers not references, causing friction for users.