Fix Anders' problem with the rendering of the foreground color. The problem with the old code was that the special highlights (internal, external, document) were added after the inbuilt highlight, and when the attributes were merged later (RenderRangeList::generateAttribute), the inbuilt highlight overwrote the other highlights, and that's why changing the foreground didn't work.

I hope I didn't break anything, but it really seems to be more reasonable to me that way.