patch 8.1.1617: no test for popup window with mask and position fixed

Problem:    No test for popup window with mask and position fixed.
Solution:   Add a couple of screenshots.  Fix deteced problems.
diff --git a/src/version.c b/src/version.c
index d05b82e..35575e2 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1617,
+/**/
     1616,
 /**/
     1615,