Order the recaptures by MVV/LVA

Almost no functional change because multiple recaptures
to same square are very rare, but neverthless it seems
the correct thing to do.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/movepick.cpp

@@ -350,7 +350,7 @@ Move MovePicker::next_move() {
            break;
 
       case CAPTURES_S6:
-          move = (curMove++)->move;
+          move = pick_best(curMove++, lastMove)->move;
           if (to_sq(move) == recaptureSquare)
               return move;
           break;