This reverts commit a7de02e052.
This did not implement the accepted proposal, and I did not sign off
on the changes. I would like a chance to review this, please.
* `doc/langref` formatting
* upgrade `.{ .path = "..." }` to `b.path("...")`
* avoid using arguments named `self`
* make `Build.Step.Id` usage more consistent
* add `Build.pathResolve`
* use `pathJoin` and `pathResolve` everywhere
* make sure `Build.LazyPath.getPath2` returns an absolute path