Issue-#1321:Warn if no patient birthdate is entered but measurements are...

... used
There's no issue, since the inner scope doesn't affect the outer one, and the hidden variable isn't needed inside.

Reusing the outer variable is OK as long as the variable is read only, or it is known and expected that the variable will change. For example:

```
function f() {
  var lis = $$('li');
  for (var i = 0; i < lis.length; ++i) {
    lis[i].observe('click', function() { alert('you clicked on item ' + i); });
  }
}
```

All items will say `you clicked on item 17`, for example, which is the final value of `i`, and not the expected counter, since there is only one `i` variable in the outer scope, shared with all the inner scopes.