This implements a standard way of describing source locations along with
printing and parsing of those locations and conversion to and from the token.Pos
forms.
Change-Id: Ibb3df0a282bc2effb0fa8bd3a51bb0d281b2ffb1
Reviewed-on: https://go-review.googlesource.com/c/tools/+/163778
Run-TryBot: Ian Cottrell <iancottrell@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
