patch 8.1.0084: user name completion does not work on MS-Windows

Problem:    User name completion does not work on MS-Windows.
Solution:   Use NetUserEnum() to get user names. (Yasuhiro Matsumoto)

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    84,
 /**/
     83,
 /**/