patch 9.0.1644: not all filetype file name matches are tested

Problem:    Not all filetype file name matches are tested.
Solution:   Add more file names to test with. (Jonas Strittmatter,
            closes #12569)
diff --git a/src/version.c b/src/version.c
index c5aa47a..5ad3b34 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1644,
+/**/
     1643,
 /**/
     1642,