Updated modules to allow for partial overrides without errors

Only define functions if they have not been defined before, e.g. in themes. This makes it possible to override parts of a module and still use the other functions.

mod/rsd_xml.php

@@ -1,7 +1,6 @@
 <?php
 
-
-
+if(! function_exists('rsd_xml_content')) {
 function rsd_xml_content(&$a) {
 	header ("Content-Type: text/xml");
 	echo '<?xml version="1.0" encoding="UTF-8"?>
@@ -21,4 +20,5 @@ function rsd_xml_content(&$a) {
  </rsd>
 	';
 die();
-}
+}
+}