syscall: fix nacl build

Timer callback does not accept now as first arg anymore.

LGTM=dave
R=golang-codereviews, dave
CC=golang-codereviews
https://golang.org/cl/126530043

src/pkg/syscall/net_nacl.go

@@ -21,7 +21,7 @@ type runtimeTimer struct {
 	i      int32
 	when   int64
 	period int64
-	f      func(int64, interface{}) // NOTE: must not be closure
+	f      func(interface{}) // NOTE: must not be closure
 	arg    interface{}
 }
 
@@ -49,7 +49,7 @@ func (t *timer) stop() {
 	stopTimer(&t.r)
 }
 
-func timerExpired(now int64, i interface{}) {
+func timerExpired(i interface{}) {
 	t := i.(*timer)
 	go func() {
 		t.q.Lock()