added missing function to abstract class

lib/dialects/query-generator.js

@@ -204,6 +204,13 @@ module.exports = (function() {
     */
     attributesToSQL: function(attributes) {
       throwMethodUndefined('attributesToSQL')
+    },
+
+    /*
+      Returns all auto increment fields of a factory.
+    */
+    findAutoIncrementField: function(factory) {
+      throwMethodUndefined('findAutoIncrementField')
     }
   }