gc: avoid 0-length C array
gc: avoid 0-length C array

R=golang-dev, ality
CC=golang-dev, rsc
http://codereview.appspot.com/5467066

Committer: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

tav/go,tav/go,tav/go,tav/go,tav/go,tav/go,tav/go