Support for showing "AUTO_INCREMENT" in "information_schema.tables"

[zimulala]

Please answer these questions before submitting your issue. Thanks!

1. What did you do?
   If possible, provide a recipe for reproducing the error.

tidb>create table t(id int auto_increment primary key, c int);
Query OK, 0 rows affected (0.11 sec)

tidb>insert into t values(1,1);
Query OK, 1 row affected (0.10 sec)

tidb>insert into t values(10000,1);
Query OK, 1 row affected (0.01 sec)

tidb>select * from t;
+-------+------+
| id    | c    |
+-------+------+
|     1 |    1 |
| 10000 |    1 |
+-------+------+
3 rows in set (0.00 sec)

select auto_increment from information_schema.tables where table_name = 't';

2. What did you expect to see?

+----------------+
| auto_increment |
+----------------+
|          30002 |
+----------------+
1 row in set (0.00 sec)

3. What did you see instead?

+----------------+
| auto_increment |
+----------------+
|             0 |
+----------------+
1 row in set (0.00 sec)