screen size was changed while the screen saver was inactive. Adjust
the positions of the daemon and the text and clip them accordingly
each time.
- Don't call set_border() too often. Some video chip may produce
flicker.
Pointed out by tony@dell.com
- Don't fill the entire screen with blank char every time the saver is
called. Blank only the part of the screen where the daemon and the
text was previously printed.