patch 8.1.1142: no test for dragging the window separators with the mouse

Problem:    No test for dragging the window separators with the mouse.
Solution:   Add a test. (Dominique Pelle, closes #4226)
diff --git a/src/version.c b/src/version.c
index 4dc55f4..a9e4ccf 100644
--- a/src/version.c
+++ b/src/version.c
@@ -772,6 +772,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1142,
+/**/
     1141,
 /**/
     1140,