Adds exception thrown by execute() method

My IDE was telling me I was trying to catch a non-existent exception, however it's clear by digging down a level that the Exception is throw by this class, so this simply annotates that.

Perhaps this should catch it and throw a QueryException?

lib/Doctrine/DBAL/Query/QueryBuilder.php

@@ -4,6 +4,7 @@
 
 use Doctrine\DBAL\Connection;
 use Doctrine\DBAL\Driver\ResultStatement;
+use Doctrine\DBAL\Exception;
 use Doctrine\DBAL\ParameterType;
 use Doctrine\DBAL\Query\Expression\CompositeExpression;
 use Doctrine\DBAL\Query\Expression\ExpressionBuilder;
@@ -200,6 +201,8 @@ public function getState()
      * Executes this query using the bound parameters and their types.
      *
      * @return ResultStatement|int
+     *
+     * @throws Exception
      */
     public function execute()
     {