macro+runtime: put all CPSification logic in r5js.ProcCall.
macro+runtime: use r5js.ProcCall#getEnv instead of direct field access.
runtime: simplify r5js.ProcCall#evalArgs.
runtime: remove unnecessary calls to r5js.datumutil#maybeWrapResult.
macro+runtime: add and use r5js.ProcCallLike#getEnv.
runtime: remove r5js.ProcCall#setEnv.
macro+runtime: remove r5js.{Branch,ProcCall}#maybeSetEnv.
runtime: rename r5js.TrampolineHelper#setNextProcCallLike => setNext.
runtime: don't call r5js.ProcCall#bindResult from PrimitiveProcedure_.
runtime: add a const suppression to r5js.Procedure#cloneWithEnv.
runtime: add abstract base class r5js.AbstractProcedure. Don't use yet.
runtime: r5js.{Procedure,PrimitiveProcedure_}: subclass AbstractProcedure.
macro+runtime: pass raw Datum to r5js.Macro#evaluate.
runtime: remove ProcedureLike impl from Procedure and PrimitiveProcedure_.
macro: r5js.Macro doesn't need to implement r5js.ProcedureLike.
runtime: r5js.Continuation doesn't need to implement r5js.ProcedureLike.
ast+runtime: remove r5js.ProcedureLike.