Some LineView simplification and tidying.

I was revamping things to support decorating line views, but that turns out to
be a giant can of worms. Better to pop things up in separate views/windows than
to try to stuff them into the main buffer area. Likely that will be more usable
anyway because then one can use normal UX like mouse scrolling &c, and one can
pop up docs or whatnot and drag them off to the side for prolonged reference.