dillon1000/react

Make implicit break/continue explicit in ReactiveFunction

Previously when converting from HIR -> ReactiveFunction we elided break/continue 
terminals in places where control would implicitly transfer to the 
break/continue target and therefore nothing has to be emitted. The one downside 
of this approach is that it makes scope analysis a bit trickier. We want to 
close scopes once we see an instruction id past the end of the scope's range, 
but these implicit breaks were causing us to miss some instruction ids. We 
compensated for this, but it's helpful to keep the representation explicit and 
discard these terminals later in codegen.