patch 8.2.1900: Vim9: command modifiers do not work

Problem:    Vim9: command modifiers do not work.
Solution:   Make most command modifiers work.
diff --git a/src/proto/usercmd.pro b/src/proto/usercmd.pro
index d7a2a6a..d24e9ad 100644
--- a/src/proto/usercmd.pro
+++ b/src/proto/usercmd.pro
@@ -14,6 +14,7 @@
 void ex_comclear(exarg_T *eap);
 void uc_clear(garray_T *gap);
 void ex_delcommand(exarg_T *eap);
-size_t add_win_cmd_modifers(char_u *buf, int *multi_mods);
+size_t add_win_cmd_modifers(char_u *buf, cmdmod_T *cmod, int *multi_mods);
+int produce_cmdmods(char_u *buf, cmdmod_T *cmod, int quote);
 void do_ucmd(exarg_T *eap);
 /* vim: set ft=c : */