patch 8.1.0698: clearing the window is used too often

Problem:    Clearing the window is used too often, causing the command line
            to be cleared when opening a tab. (Miroslav Koškár)
Solution:   Use NOT_VALID instead of CLEAR.  (suggested by Jason Franklin,
            closes #630)  Also do this for a few other places where clearing
            the screen isn't really needed.

src/version.c

@@ -799,6 +799,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    698,
 /**/
     697,
 /**/