spec: add forward links from 'method set' to where it gets used
spec: add forward links from 'method set' to where it gets used

Fixes issue 1797.

R=golang-dev, gri
CC=golang-dev
http://codereview.appspot.com/5645058

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