Support nested join operations in the FROM clause. about php-sql-parser HOT 2 CLOSED

Add support for nested table joins.  This is a MySQL extension to the ANSI join 
syntax which is omitted.  Since the goal is full MySQL syntax support, this is 
an important enhancement request.

There are plenty of examples on the listed documentation page to use as test 
cases, as well as the example included in this report.

Nested join support is checked in at revision 42:

SELECT *
    FROM (t1 LEFT JOIN t2 ON t1.a=t2.a)
         LEFT JOIN t3
         ON t2.b=t3.b OR t2.b IS NULL
Array
(
    [SELECT] => Array
        (
            [0] => Array
                (
                    [expr_type] => operator
                    [alias] => `*`
                    [base_expr] => *
                    [sub_tree] => 
                )

        )

    [FROM] => Array
        (
            [0] => Array
                (
                    [table] => (t1 LEFT JOIN t2 ON t1.a=t2.a)
                    [alias] => 
                    [join_type] => JOIN
                    [ref_type] => 
                    [ref_clause] => 
                    [base_expr] => t1 LEFT JOIN t2 ON t1.a=t2.a
                    [sub_tree] => Array
                        (
                            [0] => Array
                                (
                                    [table] => t1
                                    [alias] => t1
                                    [join_type] => JOIN
                                    [ref_type] => 
                                    [ref_clause] => 
                                    [base_expr] => 
                                    [sub_tree] => 
                                )

                            [1] => Array
                                (
                                    [table] =>  
                                    [alias] => t2
                                    [join_type] => LEFT 
                                    [ref_type] => ON
                                    [ref_clause] => t1.a=t2.a
                                    [base_expr] => 
                                    [sub_tree] => 
                                )

                        )

                )

            [1] => Array
                (
                    [table] => t3
                    [alias] => t3
                    [join_type] => LEFT 
                    [ref_type] => ON
                    [ref_clause] => t2.b=t3.b OR t2.b IS NULL
                    [base_expr] => 
                    [sub_tree] => 
                )

        )

)

t/nested.php is added to verify operation