Labeled if statement

[SheetJSDev]

A slight twist on #2243 :

/* this works in commit 5d9b405 */
foo: {
  console.log('face');
  break foo;
  console.log('this will not be executed');
}
/* This elicits `Uncaught "SyntaxError": "Cannot use the undeclared label 'bar'"` */
bar: if(true){
  console.log('face');
  break bar;
  console.log('this will not be executed');
}
console.log('swap');

[Razican]

Ideally, all these should be treated as LabeledStatement in general. This would be easier to implement once #1371 is implemented.

[SheetJSDev]

Commit 90d310b (thanks @nekevss !) fixed this example and added a representative test case.