Split the routerset code out of routerlist.c

src/or/circuitbuild.c

src/or/circuitlist.c

src/or/config.c

src/or/confparse.c

src/or/connection_edge.c

src/or/directory.c

src/or/include.am

src/or/rendclient.c

src/or/rendservice.c

src/or/router.c

src/or/routerlist.c

src/or/routerlist.h

src/or/routerset.c

src/or/routerset.h