add a function to move llist nodes around

src/lib/llist.h

@@ -306,6 +306,18 @@ LLIST_FUNC (LList llist_relocate (LList self),
             return self->next->prev = self->prev->next = self;
 );
 
+/**
+ * Move a node from one memory location to another.
+ * @param self  target of the move, must be uninitialized or empty before this move
+ * @param source source of the move, will be initialized to a empty list after this call
+ * @return self
+ */
+LLIST_FUNC (LList llist_move (LList self, LList source),
+            *self = *source;
+            llist_init (source);
+            return llist_relocate (self);
+);
+
 /**
  * Insert a node after another.
  * @param self node after which we want to insert