conversion. The tag 'TODO(DLC)[EWTS->Tibetan]' exists all over the
place. EWTS->Tibetan isn't here yet; lexing isn't here yet; this is
mainly a refactoring so that the ACIP->Tibetan code can be reused to
do EWTS->Tibetan.
I'm committing this because tests pass (it shouldn't be breaking
anything), because I want a checkpoint, and because the laptop this
sandbox was on isn't my preferred development environment.
