test: say that nilptr2.go requires 256+MB stack Fixes issue 6161.
test: say that nilptr2.go requires 256+MB stack
Fixes issue 6161.

R=golang-dev, bradfitz
CC=golang-dev
https://codereview.appspot.com/13059043

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang