added enum type validation

lib/Doctrine/Validator.php

@@ -282,6 +282,8 @@ class Doctrine_Validator extends Doctrine_Object
              case 'date':
                  $validator = self::getValidator('date');
                  return $validator->validate($var);
+             case 'enum':
+                 return is_string($var) || is_int($var);
              default:
                  return false;
          }