add todo for known issue that isn't yet critical but will be

pear/PEAR/Downloader.php

@@ -495,6 +495,8 @@ class PEAR_Downloader extends PEAR_Common
      * @param array packages that will be installed in this iteration
      * @return false|string|PEAR_Error
      * @access private
+     * @todo Add test for relation 'lt'/'le' -> make sure that the dependency requested is
+     *       in fact lower than the required value.  This will be very important for BC dependencies
      */
     function _processDependency($package, $info, $mywillinstall)
     {