patch 8.1.1769: 'shellslash' is also used for completion

Problem:    'shellslash' is also used for completion.
Solution:   Add the 'completeslash' option. (Yasuhiro Matsumoto, closes #3612)
diff --git a/src/version.c b/src/version.c
index 166b17c..2db2ee1 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1769,
+/**/
     1768,
 /**/
     1767,