Move XMPPHP from core extlibs to Xmpp plugin extlibs

plugins/Xmpp/XmppPlugin.php

@@ -34,8 +34,6 @@ if (!defined('STATUSNET')) {
     exit(1);
 }
 
-set_include_path(get_include_path() . PATH_SEPARATOR . INSTALLDIR . '/extlib/XMPPHP');
-
 /**
  * Plugin for XMPP
  *
@@ -287,7 +285,7 @@ class XmppPlugin extends ImPlugin
         switch ($cls)
         {
         case 'XMPPHP_XMPP':
-            require_once 'XMPP.php';
+            require_once $dir . '/extlib/XMPPHP/XMPP.php';
             return false;
         case 'Sharing_XMPP':
         case 'Queued_XMPP':