Bug #18239 Possible to overload internal functions with stored functions

Description:
You can create stored functions with the same name of internal functions. The behaviour is confusing.

How to repeat:
root@localhost [test]> CREATE FUNCTION now () RETURNS CHAR(10) RETURN("foo");
Query OK, 0 rows affected (0.48 sec)

root@localhost [test]> SELECT NOW();
+---------------------+
| NOW()               |
+---------------------+
| 2006-03-14 15:43:25 |
+---------------------+
1 row in set (0.08 sec)

root@localhost [test]> SELECT NOW ();
+--------+
| NOW () |
+--------+
| foo    |
+--------+
1 row in set (0.07 sec)

Suggested fix:
Read the SQL standards about it and fix it

Thank you for the bug report.

There are two separate issues :

- now() an now () can resolve to different functions,
in cases where sql_mode is not set to IGNORE_SPACE.
See related Bug#21114

- SQL defines the PATH syntax to direct name resolution for stored functions.
This SQL feature is not currently available with MySQL.

For practical reasons, the following bugs are all fixed by the same change set:
- Bug#18239
- Bug#21025
- Bug#22619

Changing to patch pending, the patch is attached in Bug#22619

This patch was applied to 5.1 only. Pushed into 5.1.13

Noted in 5.1.14 changelog.