Delay sorting of negative scored non-captures

We can do this only when needed, if we get a cut-off
before we skip sorting entirely. This reduces sorting
time of about 20%.

No functional change.

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

src/movepick.h

@@ -64,7 +64,7 @@ private:
   MoveStack ttMoves[2], killers[2];
   int phase;
   const uint8_t* phasePtr;
-  MoveStack *curMove, *lastMove, *lastBadCapture;
+  MoveStack *curMove, *lastMove, *lastGoodNonCapture, *lastBadCapture;
   Bitboard pinned;
   MoveStack moves[256], badCaptures[64];
 };