- don't draw elements with background color.
This is a small optimization for people who want to suppress the clock scale.
It can also be used to disable the seconds hand.

- move ClockPainter::scale() to the constructor & cleanup

BTW: there were people porting this screensaver to OSX and Windows:
<a href="http://www.macupdate.com/info.php/id/17884">http://www.macupdate.com/info.php/id/17884</a>; (see the review :-)

<a href="http://jaybee.cz/software/sporic-setric-obrazovky--screensaver----hodiny/">http://jaybee.cz/software/sporic-setric-obrazovky--screensaver----hodiny/</a>;