patch 8.0.0854: no redraw after terminal was closed

Problem:    No redraw after terminal was closed.
Solution:   Set typebuf_was_filled. (Yasuhiro Matsumoto, closes #1925, closes
            #1924)  Add function to check for messages even when input is
            available.
diff --git a/src/proto/os_unix.pro b/src/proto/os_unix.pro
index 46230dc..8e955aa 100644
--- a/src/proto/os_unix.pro
+++ b/src/proto/os_unix.pro
@@ -3,6 +3,7 @@
 void mch_write(char_u *s, int len);
 int mch_inchar(char_u *buf, int maxlen, long wtime, int tb_change_cnt);
 int mch_char_avail(void);
+int mch_check_messages(void);
 long_u mch_total_mem(int special);
 void mch_delay(long msec, int ignoreinput);
 int mch_stackcheck(char *p);