patch 8.2.3609: internal error when ModeChanged is triggered recursively

Problem:    Internal error when ModeChanged is triggered when v:event is
            already in use.
Solution:   Save and restore v:event if needed.
diff --git a/src/proto/misc1.pro b/src/proto/misc1.pro
index 7d4c41f..db60a6d 100644
--- a/src/proto/misc1.pro
+++ b/src/proto/misc1.pro
@@ -47,5 +47,7 @@
 char_u *get_isolated_shell_name(void);
 int path_is_url(char_u *p);
 int path_with_url(char_u *fname);
+dict_T *get_v_event(save_v_event_T *sve);
+void restore_v_event(dict_T *v_event, save_v_event_T *sve);
 void trigger_modechanged(void);
 /* vim: set ft=c : */