misc/vim:  allow only utf-8 for fileencoding (fix CL4625078).
misc/vim:  allow only utf-8 for fileencoding (fix CL4625078).

R=golang-dev, dsymonds
CC=golang-dev
http://codereview.appspot.com/4650062

Committer: David Symonds <7f6bb564ed9e580d4f0aa90d53b34578e5d24cb9@golang.org>

wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang,firebitsbr/golang-old,wesolows/golang-old