Patch review for optimization in paintop

[Cyrille Berger]

> Shouldn't the dab be cleared after use if you want to reuse the same paint
> device over and over again?
hum no because it is erase with the new data.

> In any case, 1.6 is already in rc mode, I would 
> be hesistant to add optimizations. But, for 1.6, that's your call.
that's why I asked here :) I think I will commit it to trunk, if we don't 
discover problems with it, I will apply for 1.6.1.

-- 
--- Cyrille Berger ---