runtime: reset typed dangling pointer If for whatever reason seh points into Go heap region, the dangling pointer will cause memory corruption during GC. Update issue 5193.
runtime: reset typed dangling pointer
If for whatever reason seh points into Go heap region,
the dangling pointer will cause memory corruption during GC.
Update issue 5193.

R=golang-dev, alex.brainman, iant
CC=golang-dev
https://codereview.appspot.com/8402045

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