patch 8.2.3430: no generic way to trigger an autocommand on mode change

Problem:    No generic way to trigger an autocommand on mode change.
Solution:   Add the ModeChanged autocommand event. (Magnus Gross, closes #8856)
diff --git a/src/proto/autocmd.pro b/src/proto/autocmd.pro
index 24dd1ba..d8145df 100644
--- a/src/proto/autocmd.pro
+++ b/src/proto/autocmd.pro
@@ -25,6 +25,7 @@
 int has_cmdundefined(void);
 int has_textyankpost(void);
 int has_completechanged(void);
+int has_modechanged(void);
 void block_autocmds(void);
 void unblock_autocmds(void);
 int is_autocmd_blocked(void);
diff --git a/src/proto/misc1.pro b/src/proto/misc1.pro
index 7c3e78c..4b804c9 100644
--- a/src/proto/misc1.pro
+++ b/src/proto/misc1.pro
@@ -47,4 +47,5 @@
 char_u *get_isolated_shell_name(void);
 int path_is_url(char_u *p);
 int path_with_url(char_u *fname);
+void trigger_modechanged();
 /* vim: set ft=c : */