Add a money_format function

[kangkaisen]

Add a money_format function:

mysql> select money_format(1123.456);
+------------------------+
| money_format(1123.456) |
+------------------------+
| 1,123.46               |
+------------------------+
1 row in set (0.04 sec)

mysql> select money_format(1123.45);
+-----------------------+
| money_format(1123.45) |
+-----------------------+
| 1,123.45              |
+-----------------------+
1 row in set (0.04 sec)

mysql> select money_format(1123.4);
+----------------------+
| money_format(1123.4) |
+----------------------+
| 1,123.40             |
+----------------------+
1 row in set (0.03 sec)

mysql> select money_format(11238888);
+------------------------+
| money_format(11238888) |
+------------------------+
| 11,238,888.00          |
+------------------------+
1 row in set (0.04 sec)

like PHP money_format function: https://php.net/manual/en/function.money-format.php
like Java DecimalFormat df = new DecimalFormat(",###.##");
like Mysql https://dev.mysql.com/doc/refman/5.5/en/string-functions.html#function_format