Split the rules for pre- and post- trivia, understand when we want to
do either, handle multi-line-break (in an unsatisfying way, I guess)
but otherwise lay the groundwork for thinking about it better.
Also now we don't generate lazy "Text" nodes because I thought I might
want to actually look at the newlines in the source but I don't yet.
I *can* now, though. (I can also detect EOF so there's that.)
This means that forced breaks from comments don't screw up the
following single-line things. But this still isn't right; we need to
fine tune how we represent trivia.
I think I want to start thinking about "leftmost" and "rightmost" and
it's just easier and faster if cons has an actual list in it instead
of dotted pairs.
It's weird that it counts against the line length though, like if you
were going to break you could ignore it right? At least, for the
grammar I'm working here....
Now we're cooking with gas ALTHOUGH now we have to deal with the fact
that we're gluing everything together where there *should* be spaces.
Many more improvements to come.
