patch 9.1.0908: not possible to configure :messages

Problem:  not possible to configure :messages
Solution: add the 'messagesopt' option (Shougo Matsushita)

closes: #16068

Co-authored-by: h_east <h.east.727@gmail.com>
Signed-off-by: Shougo Matsushita <Shougo.Matsu@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/proto/message.pro b/src/proto/message.pro
index 1c11444..34b3818 100644
--- a/src/proto/message.pro
+++ b/src/proto/message.pro
@@ -18,7 +18,7 @@
 char *msg_trunc_attr(char *s, int force, int attr);
 char_u *msg_may_trunc(int force, char_u *s);
 int delete_first_msg(void);
-void check_msg_hist(void);
+int messagesopt_changed(void);
 void ex_messages(exarg_T *eap);
 void msg_end_prompt(void);
 void wait_return(int redraw);