Fails with duplicate var declarations

[Rich-Harris]

This fails:

function x () {
  for ( var i = 0; i < 10; i += 1 ) {
    console.log(i);
  }

  for ( var i = 0; i < 10; i += 1 ) {
    console.log(i);
  }
}

Separately, this could be better optimised:

var i = 1;
var i = 2;

[Rich-Harris]

Fixed in 0.3.2