fix build: remove non-portable test case
fix build: remove non-portable test case

On a 32bit machine, the big.Words are only 32bit.

R=rsc
CC=golang-dev
http://codereview.appspot.com/4561055

dsriram/golang,pombredanne/go-deleteme,apparentlymart/golang,ssrl/go,dsriram/golang,tv42/old-go,tv42/old-go,dsriram/golang,tv42/old-go,dsriram/golang,ssrl/go,pombredanne/go-deleteme,ssrl/go,apparentlymart/golang,pombredanne/go-deleteme,apparentlymart/golang,gnanderson/go,gnanderson/go,pombredanne/go-deleteme,ssrl/go,pombredanne/go-deleteme,gnanderson/go,apparentlymart/golang,dsriram/golang,dsriram/golang,gnanderson/go,ssrl/go,apparentlymart/golang,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,ssrl/go,tv42/old-go,gnanderson/go,apparentlymart/golang,gnanderson/go,pombredanne/go-deleteme,gnanderson/go,dsriram/golang,ssrl/go,apparentlymart/golang,tv42/old-go