patch 8.1.1221: filtering does not work when listing marks

Problem:    Filtering does not work when listing marks.
Solution:   Implement filtering marks. (Marcin Szamotulski, closes #3895)
diff --git a/src/version.c b/src/version.c
index 9fe5d2d..c65c541 100644
--- a/src/version.c
+++ b/src/version.c
@@ -768,6 +768,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1221,
+/**/
     1220,
 /**/
     1219,