Distfile has been rerolled without version bump. The new release include some
fixes for the case when SDL doesn't contain GL support built in, so bump
PORTREVISION to let users know that update is necessary.
Update checksum. The only change between old and new versions is fixed a bug
in joystick support, but AFAIK SDL port doesn't support joystick on FreeBSD,
so no PORTREVISION bump was performed.