op: remove operation list argument from MacroOp.Add

The ability to invoke other operation lists belongs in the new CallOp.

While we're here, make MacroOp.Add use a pointer receiver to match the
other methods.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

op/clip/clip.go

@@ -40,7 +40,7 @@ type Op struct {
 }
 
 func (p Op) Add(o *op.Ops) {
-	p.macro.Add(o)
+	p.macro.Add()
 	data := o.Write(opconst.TypeClipLen)
 	data[0] = byte(opconst.TypeClip)
 	bo := binary.LittleEndian