patch 8.1.2301: MS-Windows GUI: drawing error when background color changes

Problem:    MS-Windows GUI: drawing error when background color changes.
Solution:   Implement gui_mch_new_colors(). (Simon Sadler)
diff --git a/src/version.c b/src/version.c
index 13d8616..b916434 100644
--- a/src/version.c
+++ b/src/version.c
@@ -742,6 +742,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2301,
+/**/
     2300,
 /**/
     2299,