Fixed incorrect docblock for setLastRealOrderId() and getLastRealOrderId() (#2752)

Author: kiatng

app/code/core/Mage/Checkout/Model/Session.php

@@ -58,8 +58,8 @@
  * @method int getLastQuoteId()
  * @method $this setLastQuoteId(int $value)
  * @method $this unsLastQuoteId()
- * @method int getLastRealOrderId()
- * @method $this setLastRealOrderId(int $value)
+ * @method string getLastRealOrderId()
+ * @method $this setLastRealOrderId(string $value)
  * @method $this unsLastRealOrderId()
  * @method int getLastRecurringProfileIds()
  * @method $this setLastRecurringProfileIds(array $value)