patch 8.0.1815: crash with terminal window and with 'lazyredraw' set

Problem:    Still a crash with terminal window and with 'lazyredraw' set.
            (Antoine)
Solution:   Do not wipe out the buffer when updating the screen.
diff --git a/src/proto/terminal.pro b/src/proto/terminal.pro
index 93c6ab5..25f9647 100644
--- a/src/proto/terminal.pro
+++ b/src/proto/terminal.pro
@@ -20,6 +20,7 @@
 int terminal_loop(int blocking);
 void term_job_ended(job_T *job);
 void term_channel_closed(channel_T *ch);
+void term_check_channel_closed_recently(void);
 int term_do_update_window(win_T *wp);
 void term_update_window(win_T *wp);
 int term_is_finished(buf_T *buf);