Brushes and notify

[Boudewijn Rempt]

I've copied some code from another Qt-based paint application, Perico by Peter 
Jodda, to kis_tool_brush.cc to see whether that would be faster/better than 
any of the other connect-the-dots methods I used. It is, some, but the brush 
is still not quite completely usable. 

The notify() method was very slow, and I was calling notify for every dab with 
the brush; now, if mouse moves make it necessary to paint a line, I only 
notify when the line is done. But it's still pretty slow.

-- 
Boudewijn Rempt | http://www.valdyas.org/fading/index.cgi