Analyzer and emitter support for rest-params in fn args

This may or may not be moved out of the compiler codebase once we implement
proper destructuring for fn args and let/loop bindings as macros over core
fn*/let*/loop* primitives with limited destructuring capabilities, but it's
helpful to have it in place in the meantime.
Emit temp rebindings when emitting recur nodes
Fix emission of variable-arity functions
Restore desugaring of interop syntax