Explore using arranged functions to fill in for unsupported type reductions

[PathogenDavid]

One of the interesting features of Clang's function arrangement API is that it gives you the lower-level representation of various types. (For instance, a reference type becomes a pointer.)

We don't take advantage of this feature right now, but in theory we could use it as a fallback during type reduction to see if the underlying LLVM-friendly representation of the type is something we're able to process even when we don't understand the higher-level C++ type.