patch 8.2.3356: adding many text properties requires a lot of function calls

Problem:    Adding many text properties requires a lot of function calls.
Solution:   Add the prop_add_list() function. (Yegappan Lakshmanan,
            closes #8751)
diff --git a/src/proto/textprop.pro b/src/proto/textprop.pro
index 8a4a22f..72a900b 100644
--- a/src/proto/textprop.pro
+++ b/src/proto/textprop.pro
@@ -1,6 +1,7 @@
 /* textprop.c */
 int find_prop_type_id(char_u *name, buf_T *buf);
 void f_prop_add(typval_T *argvars, typval_T *rettv);
+void f_prop_add_list(typval_T *argvars, typval_T *rettv);
 void prop_add_common(linenr_T start_lnum, colnr_T start_col, dict_T *dict, buf_T *default_buf, typval_T *dict_arg);
 int get_text_props(buf_T *buf, linenr_T lnum, char_u **props, int will_change);
 int count_props(linenr_T lnum, int only_starting);