patch 8.1.0466: autocmd test fails

Problem:    Autocmd test fails.
Solution:   Do call inchar() when flushing typeahead.
diff --git a/src/proto/getchar.pro b/src/proto/getchar.pro
index aac522f..0733662 100644
--- a/src/proto/getchar.pro
+++ b/src/proto/getchar.pro
@@ -5,7 +5,7 @@
 int stuff_empty(void);
 int readbuf1_empty(void);
 void typeahead_noflush(int c);
-void flush_buffers(int flush_typeahead);
+void flush_buffers(flush_buffers_T flush_typeahead);
 void ResetRedobuff(void);
 void CancelRedo(void);
 void saveRedobuff(save_redo_T *save_redo);