message: Add API for binding's name
diff: @@ -20,6 +20,7 @@ pub trait RBind {
  fn mark_return(&mut self);
  fn name(&self) -> String;
  + fn set_name(&mut self, String);
  fn is_register(&self) -> bool;
  fn mark_register(&mut self, String);
  @@ -254,6 +255,10 @@ impl<T: Clone + fmt::Debug> RBind for Binding<T> {
  self.named.clone().unwrap_or_else(String::new)
  }
  + fn set_name(&mut self, name: String) {
  + self.named = Some(name);
  + }
  +
  fn is_register(&self) -> bool {
  match self.vloc {
  VarLocation::Register { .. } => true,
  