go.tools/go/types: clearer documentation
go.tools/go/types: clearer documentation

(Follow-up of CL feedback.)

R=adonovan
CC=golang-dev
https://golang.org/cl/13333047

nicot/tools,jdhenke/tools,dmitris/tools,runcom/tools,runcom/tools,glasser/golang-tools,argandas/tools,syreclabs/go-tools,jdhenke/tools,matryer/tools,jdhenke/tools,sshetty10/tools,runcom/tools,golang/tools,dmitris/tools,josharian/tools,syreclabs/go-tools,argandas/tools,cmars/tools,cw2018/tools,sshetty10/tools,magiccao/tools,golang/tools,syreclabs/go-tools,jdhenke/tools,4ad/tools,maddyonline/tools,4ad/tools,syreclabs/go-tools,cw2018/tools,syreclabs/go-tools,maddyonline/tools,golang/tools,sshetty10/tools,cmars/tools,runcom/tools,syreclabs/go-tools,josharian/tools,golang/tools,dmitris/tools,magiccao/tools,cmars/tools,matryer/tools,golang/tools,springning/tools,matryer/tools,josharian/tools,springning/tools,sshetty10/tools,argandas/tools,nicot/tools,argandas/tools,dmitris/tools,cmars/tools,cw2018/tools,nicot/tools,4ad/tools,magiccao/tools,maddyonline/tools,springning/tools,cw2018/tools,matryer/tools,josharian/tools,glasser/golang-tools,glasser/golang-tools,glasser/golang-tools,springning/tools,maddyonline/tools,magiccao/tools,nicot/tools