make String work on Position values, to enable
make String work on Position values, to enable

	fmt.Printf("%s: %s\n", expr.Pos(), message);

R=gri
DELTA=15  (1 added, 3 deleted, 11 changed)
OCL=34706
CL=34708

wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang,wesolows/golang,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang-old