patch 8.1.1561: popup_setoptions() is not implemented yet

Problem:    Popup_setoptions() is not implemented yet.
Solution:   Implement popup_setoptions().  Also add more fields to
            popup_getoptions().

src/dict.c

@@ -447,6 +447,27 @@ dict_add_list(dict_T *d, char *key, list_T *list)
     return OK;
 }
 
+/*
+ * Add a callback to dictionary "d".
+ * Returns FAIL when out of memory and when key already exists.
+ */
+    int
+dict_add_callback(dict_T *d, char *key, callback_T *cb)
+{
+    dictitem_T	*item;
+
+    item = dictitem_alloc((char_u *)key);
+    if (item == NULL)
+	return FAIL;
+    put_callback(cb, &item->di_tv);
+    if (dict_add(d, item) == FAIL)
+    {
+	dictitem_free(item);
+	return FAIL;
+    }
+    return OK;
+}
+
 /*
  * Initializes "iter" for iterating over dictionary items with
  * dict_iterate_next().