arguments are mangled in continuations

[maxtaco]

As reported by @devongovett

fn = ->
  await setTimeout defer(), 1000
  alert arguments[0]

fn 'hi'

Two options, either use CS's pretty apply(this, arguments) technique, or do the ugly thing, with is to set var _arguments = arguments, as how _this = this is handled.

[maxtaco]

Now closed, though potentially we need a cleaner solution.