patch 8.2.0015: not all modeline variants are tested

Problem:    Not all modeline variants are tested.
Solution:   Add modeline tests. (Dominique Pelle, closes #5369)
diff --git a/src/version.c b/src/version.c
index 713d06c..ed57cd8 100644
--- a/src/version.c
+++ b/src/version.c
@@ -743,6 +743,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    15,
+/**/
     14,
 /**/
     13,