* rework the inline boxes ownership/deletion model, introduce dirtying of line boxes so has to be able to selectively update on layout instead of rebuilding everything, replace RenderText's vectors with linked lists.

Lot of bits, pieces and ideas taken from WebCore and elaborated upon.

* some serious optimization work on positioned objects. This makes KHTML quite fast on cpu intensive DHTML/Javascript showcases.

Some annecdotal timings for e.g:
<a href="http://nontroppo.org/timer/progressive_raytracer.html">http://nontroppo.org/timer/progressive_raytracer.html</a>;

KHTML/KJS 25 sec.
Opera 9.0 37 sec.
IE7(wine) 54 sec.
WebKitQt 115 sec.
FF2.0 640 sec.