patch 8.0.0468: after aborting an Ex command g< does not work

Problem:    After aborting an Ex command g< does not work. (Marcin
            Szamotulski)
Solution:   Postpone clearing scrollback messages to until the command line
            has been entered.  Also fix that the screen isn't redrawn if after
            g< the command line is cancelled.
diff --git a/src/proto/message.pro b/src/proto/message.pro
index 9a79f14..8d9ac71 100644
--- a/src/proto/message.pro
+++ b/src/proto/message.pro
@@ -52,7 +52,9 @@
 void msg_puts_attr(char_u *s, int attr);
 int message_filtered(char_u *msg);
 void may_clear_sb_text(void);
-void clear_sb_text(void);
+void sb_text_start_cmdline(void);
+void sb_text_end_cmdline(void);
+void clear_sb_text(int all);
 void show_sb_text(void);
 void msg_sb_eol(void);
 int msg_use_printf(void);