runtime: fix vet warning about println

lfstack.go:19: println call ends with newline

Change-Id: I2a903eef80a5300e9014999c2f0bc5d40ed5c735
Reviewed-on: https://go-review.googlesource.com/16836
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>

src/runtime/lfstack.go

@@ -16,7 +16,7 @@ func lfstackpush(head *uint64, node *lfnode) {
 	node.pushcnt++
 	new := lfstackPack(node, node.pushcnt)
 	if node1, _ := lfstackUnpack(new); node1 != node {
-		println("runtime: lfstackpush invalid packing: node=", node, " cnt=", hex(node.pushcnt), " packed=", hex(new), " -> node=", node1, "\n")
+		print("runtime: lfstackpush invalid packing: node=", node, " cnt=", hex(node.pushcnt), " packed=", hex(new), " -> node=", node1, "\n")
 		throw("lfstackpush")
 	}
 	for {