Question about something in ports/CHANGES file (re: upgrading MySQL)

[Paul D. Schmidt]

Where can I find more information about the following? (Taken
from /usr/ports/CHANGES)

20040204:
    ...
    The ports system now supports MySQL 3.23, 4.0, 4.1, and 5.0.
    Also, the ability to scale to newer versions was also but in
    place.
    ...

I don't see anything in the mysql40-server Makefile that has anything
to do with upgrades...where else should I look?  I'm trying to convert
from a 3.23 system.

Thanks,
-Paul