patch 8.2.3040: GUI: dropping files not tested

Problem:    GUI: dropping files not tested.
Solution:   Add test_gui_drop_files() and tests. (Yegappan Lakshmanan,
            closes #8434)
diff --git a/src/version.c b/src/version.c
index 83c7460..bf33312 100644
--- a/src/version.c
+++ b/src/version.c
@@ -756,6 +756,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3040,
+/**/
     3039,
 /**/
     3038,