patch 8.2.3271: Vim9: cannot use :command or :au with block in :def function

Problem:    Vim9: cannot use :command or :au with a block in a :def function.
Solution:   Recognize the start of the block.
diff --git a/src/proto/ex_docmd.pro b/src/proto/ex_docmd.pro
index d22d406..419d004 100644
--- a/src/proto/ex_docmd.pro
+++ b/src/proto/ex_docmd.pro
@@ -9,6 +9,7 @@
 char_u *getline_peek(char_u *(*fgetline)(int, void *, int, getline_opt_T), void *cookie);
 char *ex_errmsg(char *msg, char_u *arg);
 int checkforcmd(char_u **pp, char *cmd, int len);
+int checkforcmd_noparen(char_u **pp, char *cmd, int len);
 int parse_command_modifiers(exarg_T *eap, char **errormsg, cmdmod_T *cmod, int skip_only);
 int has_cmdmod(cmdmod_T *cmod);
 int cmdmod_error(void);