Prefer Passing by Reference over Breaking Chaining in DBTNG

Before:

$query = db_select("baz", "baz");
$join_name = $query->join("foo", "foo", "foo.bar = baz.quux");
//... using $join_name
$result = $query->execute();

After:

$result = db_select("baz", "baz");
  ->join("foo", "foo", $join_name, "foo.bar = baz.quux")
  //... using $join_name
  ->execute()
;