misc/vim: update installation instructions to work better with some Linux distributions.
misc/vim: update installation instructions to work better with some Linux distributions.

Fixes issue 3308.

R=golang-dev, minux.ma
CC=golang-dev
https://codereview.appspot.com/7301086

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