FROM I_S

Issue:
------
There is a difference in the field type created when the
following DDLs are used:

1) CREATE TABLE t0 AS SELECT NULL;
2) CREATE TABLE t0 AS SELECT GREATEST(NULL,NULL);

The first statement creates field of type Field_string and
the second one creates a field of type Field_null.

This creates a problem when the query mentioned in this bug
is used. Since the null_ptr is calculated differently for
Field_null.

Solution:
---------
When there is a function returning null in the select list
as mentioned above, the field should be of type
Field_string.

This was fixed in 5.6+ as part of Bug#14021323. This is a
backport to mysql-5.5.

An incorrect comment in innodb_bug54044.test has been
corrected in all versions.