go.tools/ssa: unexport Register.
go.tools/ssa: unexport Register.

R=gri
CC=golang-dev
https://golang.org/cl/14672043

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