Fix implementation of BufferedStatement

Implement the Iterator interface directly. This allows the statement to
actually buffer results between iterations. It also solves the pierce
through problems that arise when statements are used with Collection.

src/Database/Schema/SqliteSchema.php

@@ -507,8 +507,9 @@ public function truncateTableSql(TableSchema $schema)
      */
     public function hasSequences()
     {
-        $result = $this->_driver
-            ->prepare('SELECT 1 FROM sqlite_master WHERE name = "sqlite_sequence"');
+        $result = $this->_driver->prepare(
+            'SELECT 1 FROM sqlite_master WHERE name = "sqlite_sequence"'
+        );
         $result->execute();
         $this->_hasSequences = (bool)$result->rowCount();
         $result->closeCursor();