go.tools/cmd/godoc: add handlers for new sub-repo paths
go.tools/cmd/godoc: add handlers for new sub-repo paths

Fixes golang/go#9009.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/162470043

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