d95c321062
rename 'try' intrinsic to 'catch_unwind' The intrinsic has nothing to do with `try` blocks, and corresponds to the stable `catch_unwind` function, so this makes a lot more sense IMO. Also rename Miri's special function while we are at it, to reflect the level of abstraction it works on: it's an unwinding mechanism, on which Rust implements panics.
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.