patch 8.2.0018: :join does not add white space where it should

Problem:    :join does not add white space where it should. (Zdenek Dohnal)
Solution:   Handle joining multiple lines propely.
diff --git a/src/version.c b/src/version.c
index c11710a..65924cd 100644
--- a/src/version.c
+++ b/src/version.c
@@ -743,6 +743,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    18,
+/**/
     17,
 /**/
     16,