patch 9.0.1643: filetype detection fails if file name ends in many '~'

Problem:    Filetype detection fails if file name ends in many '~'.
Solution:   Strip multiple '~' at the same time. (closes #12553)
diff --git a/src/version.c b/src/version.c
index 1d29427..c5aa47a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1643,
+/**/
     1642,
 /**/
     1641,