patch 9.0.0592: display not cleared when scrolling back in messages

Problem:    Display not cleared when scrolling back in messages, a background
            color is set and t_ut is empty.
Solution:   Clear to the end of the display if needed. (closes #8973)

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    592,
 /**/
     591,
 /**/