Changes in release 3.22.18
--------------------------
* Fixes a fatal problem in 3.22.17 on Linux; After `shutdown' all
threads didn't die properly.
* Added option `-O flush_time=#' to `mysqld'. This is mostly useful
on Windows and tells how often MySQL should close all unused
tables and flush all updated tables to disk.
* Fixed problem that a `VARCHAR' column compared with `CHAR' column
didn't use keys efficiently.