- Adds 'go vet -json' and 'go vet -c=1' flags
- Removes the pkgfact analyzer, included by mistake.

Change-Id: Id3f1879af479efc567ea0508a1de7a37db5bee89
Reviewed-on: https://go-review.googlesource.com/c/149961
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Michael Matloob <matloob@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>