patch 8.1.0603: the :stop command is not tested

Problem:    The :stop command is not tested.
Solution:   Test :stop using a terminal window.
diff --git a/src/version.c b/src/version.c
index f9154cd..c73a3ed 100644
--- a/src/version.c
+++ b/src/version.c
@@ -800,6 +800,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    603,
+/**/
     602,
 /**/
     601,