[testlib] fix page validator selection. Closes #2869456 * use a validator that checks XML well-formness for the html5 doctype (as a convenient side-effect, it does not choke on e.g. a canvas tag like the HTMLParser does) * use a DTD validator if there is an xml declaration * else use the HTMLValidator

$(document).ready(function() {

  module("air");

  test("test 1", function() {
      equals(a, 4);
  });

});