Make the hold marker' in Guess accessible from the keyboard (H' key, for want

of a better idea).

[originally from svn r6004]

guess.c

@@ -684,6 +684,9 @@ static game_state *make_move(game_state *from, game_ui *ui, game_drawstate *ds,
             set_peg(&from->params, ui, ui->peg_cur, ui->colour_cur+1);
             ret = from;
         }
+    } else if (button == 'H' || button == 'h') {
+        ui->holds[ui->peg_cur] = 1 - ui->holds[ui->peg_cur];
+        ret = from;
     }
     return ret;
 }