- clarify vector comment

- adjusted a test to check claim

R=rsc
DELTA=3  (2 added, 0 deleted, 1 changed)
OCL=34454
CL=34456

src/pkg/container/vector/vector.go

@@ -12,6 +12,7 @@ type Element interface {}
 
 
 // Vector is the container itself.
+// The zero value for Vector is an empty vector ready to use.
 type Vector struct {
 	a []Element
 }

src/pkg/container/vector/vector_test.go

@@ -52,7 +52,7 @@ func TestAccess(t *testing.T) {
 
 func TestInsertDeleteClear(t *testing.T) {
 	const n = 100;
-	a := New(0);
+	var a Vector;
 
 	for i := 0; i < n; i++ {
 		if a.Len() != i { t.Errorf("A) wrong len %d (expected %d)", a.Len(), i) }
@@ -189,6 +189,7 @@ func TestDo(t *testing.T) {
 	}
 }
 
+
 func TestIter(t *testing.T) {
 	const Len = 100;
 	x := New(Len);