patch 8.2.3617: ":verbose pwd" does not mention 'autochdir' was applied

Problem:    ":verbose pwd" does not mention 'autochdir' was applied.
Solution:   Remember the last chdir was done by 'autochdir'.  (issue #9142)
diff --git a/src/globals.h b/src/globals.h
index 5c54130..90998d8 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -832,6 +832,7 @@
 #if defined(FEAT_AUTOCHDIR)
 EXTERN int	test_autochdir INIT(= FALSE);
 #endif
+EXTERN char	*last_chdir_reason INIT(= NULL);
 #if defined(EXITFREE)
 EXTERN int	entered_free_all_mem INIT(= FALSE);
 				// TRUE when in or after free_all_mem()