refactor & make jshint happy

Author: Narretz

src/Angular.js

@@ -1942,7 +1942,7 @@ function stringify(value) {
       value = '' + value;
       break;
     default:
-      if (isFunction(value.toString) && value.toString !== Object.prototype.toString && !isArray(value)) {
+      if (hasCustomToString(value) && !isArray(value)) {
         value = value.toString();
       } else {
         value = toJson(value);

src/ngMessageFormat/messageFormatCommon.js

@@ -9,7 +9,8 @@ var $interpolateMinErr = window['angular']['$interpolateMinErr'];
 
 var noop = window['angular']['noop'],
     isFunction = window['angular']['isFunction'],
-    toJson = window['angular']['toJson'];
+    toJson = window['angular']['toJson'],
+    isArray = window['angular']['isArray'];
 
 function stringify(value) {
   if (value == null) { // null || undefined