time.NewTicker: panic for intervals <= 0. Not absolutely certain it's right to do this, but since there's no error value coming back, it seems reasonable.
time.NewTicker: panic for intervals <= 0.
Not absolutely certain it's right to do this, but since there's
no error value coming back, it seems reasonable.

Fixes issue 1392.

R=rsc, adg
CC=golang-dev
http://codereview.appspot.com/3896042

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