Fix XML renderer crash

[Sei-Lisa]

The XML renderer crashed because two styler properties it expected to be public are now private. Fixed by adding the corresponding getXXX functions to the styler.

[Sei-Lisa]

Test case:

<?php
include('class.geshi.php');
require_once GESHI_CLASSES_ROOT.'class.geshirenderer.php';
require_once GESHI_RENDERERS_ROOT.'class.geshirendererxml.php';

$geshi = new GeSHi('var a = 1.0;
// comment
function x() {
  var b = Math.PI;
  var c = "string\\n" + \'string\';
  return b;
}
', 'javascript');
$geshi->setRenderer(new GeSHiRendererXML);
echo $geshi->parseCode();

Without patch:
Fatal error: Cannot access private property GeSHiStyler::$language in /<path>/geshi/classes/renderers/class.geshirendererxml.php on line 129

With patch, output is generated but it includes css="Array" everywhere in the output, as expected as per issue #3.