patch 8.0.0593: duplication of code for adding a list or dict return value

Problem:    Duplication of code for adding a list or dict return value.
Solution:   Add rettv_dict_set() and rettv_list_set(). (Yegappan Lakshmanan)
diff --git a/src/proto/dict.pro b/src/proto/dict.pro
index 61f4dfa..2a76263 100644
--- a/src/proto/dict.pro
+++ b/src/proto/dict.pro
@@ -1,6 +1,7 @@
 /* dict.c */
 dict_T *dict_alloc(void);
 int rettv_dict_alloc(typval_T *rettv);
+void rettv_dict_set(typval_T *rettv, dict_T *d);
 void dict_unref(dict_T *d);
 int dict_free_nonref(int copyID);
 void dict_free_items(int copyID);
diff --git a/src/proto/list.pro b/src/proto/list.pro
index 56f0ddc..fe54bab 100644
--- a/src/proto/list.pro
+++ b/src/proto/list.pro
@@ -4,6 +4,7 @@
 void list_fix_watch(list_T *l, listitem_T *item);
 list_T *list_alloc(void);
 int rettv_list_alloc(typval_T *rettv);
+void rettv_list_set(typval_T *rettv, list_T *l);
 void list_unref(list_T *l);
 int list_free_nonref(int copyID);
 void list_free_items(int copyID);