roken: getuserinfo WIN32 fix username string termination

95eb83c424 ("roken: Add roken_get_username() and friends")
failed to copy the username C-String NUL terminator.  As a result
a "DOMAIN\user" is returned as "userIN\user".

Change-Id: I10027e4eef18364074eecf385fa9fab1ae68dbe7

lib/roken/getuserinfo.c

@@ -230,7 +230,7 @@ roken_get_username(char *user, size_t usersz)
         p = strchr(user, '\\');
         if (p != NULL) {
             p++;
-            memmove(user, p, strlen(p));
+            memmove(user, p, strlen(p) + 1);
         }
         return user;
     } else {