patch 8.1.0159: completion for user names does not work for a prefix.

Problem:    Completion for user names does not work if a prefix is also a full
            matching name. (Nazri Ramliy)
Solution:   Accept both full and partial matches. (Dominique Pelle)

src/ex_docmd.c

@@ -3764,7 +3764,7 @@ set_one_cmd_context(
 	     * A full match ~user<Tab> will be replaced by user's home
 	     * directory i.e. something like ~user<Tab> -> /home/user/ */
 	    if (*p == NUL && p > xp->xp_pattern + 1
-				       && match_user(xp->xp_pattern + 1) == 1)
+				       && match_user(xp->xp_pattern + 1) >= 1)
 	    {
 		xp->xp_context = EXPAND_USER;
 		++xp->xp_pattern;

src/misc1.c

@@ -4827,7 +4827,8 @@ get_users(expand_T *xp UNUSED, int idx)
  * 1 if name partially matches the beginning of a user name.
  * 2 is name fully matches a user name.
  */
-int match_user(char_u* name)
+    int
+match_user(char_u *name)
 {
     int i;
     int n = (int)STRLEN(name);

src/version.c

@@ -789,6 +789,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    159,
 /**/
     158,
 /**/