patch 8.1.1175: no test for dragging a tab and double click for new tab

Problem:    No test for dragging a tab with the mouse and for creating a new
            tab by double clicking in the tabline.
Solution:   Add two tests. (Dominique Pelle, closes #4258)
diff --git a/src/version.c b/src/version.c
index 54c15f3..fb35556 100644
--- a/src/version.c
+++ b/src/version.c
@@ -772,6 +772,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1175,
+/**/
     1174,
 /**/
     1173,