go.toools/go/types: clearer comment (per adonovan)
go.toools/go/types: clearer comment (per adonovan)

R=adonovan
CC=golang-dev
https://codereview.appspot.com/40860045

lattera/go.tools,lattera/go.tools,lattera/go.tools,karmakaze/go.tools,karmakaze/go.tools,karmakaze/go.tools,chenjianlong/go.tools,karmakaze/go.tools,karmakaze/go.tools,chenjianlong/go.tools,chenjianlong/go.tools