Add a type_id intrinsic

Closes #9913
Remove unnecessary unwind messages

Now that the type_id intrinsic is working across crates, all of these
unnecessary messages can be removed to have the failure type for a task truly be
~Any and only ~Any
auto merge of #10182 : alexcrichton/rust/typeid-intrinsic, r=nikomatsakis

This isn't quite as fancy as the struct in #9913, but I'm not sure we should be exposing crate names/hashes of the types. That being said, it'd be pretty easy to extend this (the deterministic hashing regardless of what crate you're in was the hard part).