misc/cgo/test: fix a gcc warning See https://code.google.com/p/go/issues/detail?id=5227#c16.
misc/cgo/test: fix a gcc warning
See https://code.google.com/p/go/issues/detail?id=5227#c16.

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/8833044

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