repl+runtime+test: rename some local vars to "platform".
eval: document that r5js.Evaluator#evaluate can throw r5js.Errors.
Makefile: fix compilation for html5 port.
eval+test: remove over-complex r5js.EvalAdapter class (but keep statics).
platform+repl: no need to pass entire evaluator into Platform#getTerminal.
repl: avoid using r5js.Evaluator#withPorts in r5js.repl.main.
Makefile: fix node-repl target.
boot+eval+repl+test: make r5js.Evaluator async. Add separate sync interface.