patch 8.1.1683: dictionary with string keys is longer than needed

Problem:    Dictionary with string keys is longer than needed.
Solution:   Use *{key: val} for literaly keys.
diff --git a/src/proto/dict.pro b/src/proto/dict.pro
index 3d31347..c133523 100644
--- a/src/proto/dict.pro
+++ b/src/proto/dict.pro
@@ -28,7 +28,7 @@
 varnumber_T dict_get_number(dict_T *d, char_u *key);
 varnumber_T dict_get_number_check(dict_T *d, char_u *key);
 char_u *dict2string(typval_T *tv, int copyID, int restore_copyID);
-int dict_get_tv(char_u **arg, typval_T *rettv, int evaluate);
+int dict_get_tv(char_u **arg, typval_T *rettv, int evaluate, int literal);
 void dict_extend(dict_T *d1, dict_T *d2, char_u *action);
 dictitem_T *dict_lookup(hashitem_T *hi);
 int dict_equal(dict_T *d1, dict_T *d2, int ic, int recursive);