patch 8.1.1223: middle mouse click test fails without a clipboard

Problem:    Middle mouse click test fails without a clipboard.
Solution:   Check if the clipboard can be used. (Dominique Pelle, Christian
            Brabandt)  Also use WorkingClipboard() instead of checking for the
            "clipboard" feature.

src/version.c

@@ -767,6 +767,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1223,
 /**/
     1222,
 /**/