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.
diff --git a/src/version.c b/src/version.c
index 8c5679e..bb3581c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    610,
+/**/
     609,
 /**/
     608,