misc/emacs: make _ a word symbol
misc/emacs: make _ a word symbol

Fixes issue 655.

R=rsc, aclements
CC=golang-dev
http://codereview.appspot.com/1981041

Committer: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

tav/go,tav/go,tav/go,tav/go,tav/go,tav/go,tav/go