patch 8.2.2898: QuitPre and ExitPre not triggered when GUI window is closed

Problem:    QuitPre and ExitPre not triggered when GUI window is closed.
Solution:   Call before_quit_autocmds(). (closes #8242)
diff --git a/src/proto/ex_docmd.pro b/src/proto/ex_docmd.pro
index 8481063..959f209 100644
--- a/src/proto/ex_docmd.pro
+++ b/src/proto/ex_docmd.pro
@@ -7,13 +7,13 @@
 void *getline_cookie(char_u *(*fgetline)(int, void *, int, getline_opt_T), void *cookie);
 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 parse_command_modifiers(exarg_T *eap, char **errormsg, cmdmod_T *cmod, int skip_only);
 int has_cmdmod(cmdmod_T *cmod);
 int cmdmod_error(void);
 void apply_cmdmod(cmdmod_T *cmod);
 void undo_cmdmod(cmdmod_T *cmod);
 int parse_cmd_address(exarg_T *eap, char **errormsg, int silent);
-int checkforcmd(char_u **pp, char *cmd, int len);
 char_u *skip_option_env_lead(char_u *start);
 char_u *find_ex_command(exarg_T *eap, int *full, int (*lookup)(char_u *, size_t, int cmd, cctx_T *), cctx_T *cctx);
 int modifier_len(char_u *cmd);
@@ -33,6 +33,7 @@
 char_u *check_nextcmd(char_u *p);
 char_u *get_command_name(expand_T *xp, int idx);
 void not_exiting(void);
+int before_quit_autocmds(win_T *wp, int quit_all, int forceit);
 void ex_quit(exarg_T *eap);
 void tabpage_close(int forceit);
 void tabpage_close_other(tabpage_T *tp, int forceit);