Changes in release 3.21.31
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* Fixed a sign extension problem for the `TINYINT' type on Irix.
* Fixed problem with `LEFT("constant_string",function)'.
* Fixed problem with `FIND_IN_SET()'.
* `LEFT JOIN' core dumped if the second table is used with a constant
`WHERE/ON' expression that uniquely identifies one record.
* Fixed problems with `DATE_FORMAT()' and incorrect dates.
`DATE_FORMAT()' now ignores `'%'' to make it possible to extend it
more easily in the future.