patch 8.0.0610: the screen is redrawn when default 'background' is detected

Problem:    The screen is redrawn when t_BG is set and used to detect the
            value for 'background'.
Solution:   Don't redraw when the value of 'background' didn't change.

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    610,
 /**/
     609,
 /**/