this fixes several issues

• emitting name is illegal if if name is a javascript keyword ([Emit] New should not be used as a name of function expression when emitting accessors #43)
• property function name should not be in scope inside the function body:
  Consider this code

var x = 1
var y = { x() { x++; } }; 

Here x in x++ should refer to the var x.
Traceur emits it as

  var x = 1;
  var y = {x: function() {
      x++;
    }};