Convert handling of tt moves and killers to standard form

Use the same way of loop along the move list used for
the others move kinds so to be consistent in get_next_move()

And a bit of the usual clean up too, but just a bit.

It is even a bit (+0.3%) faster now. ;-)

No functional change.

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

src/movepick.h

@@ -79,12 +79,12 @@ private:
 
   const Position& pos;
   const History& H;
-  Move ttMoves[2], killers[2];
-  const MovegenPhaseT* phasePtr;
-  int phase, movesPicked, numOfBadCaptures;
+  MoveStack ttMoves[2], killers[2];
   bool finished;
-  Bitboard dc, pinned;
+  int numOfBadCaptures, phase;
+  const MovegenPhaseT* phasePtr;
   MoveStack *curMove, *lastMove;
+  Bitboard dc, pinned;
   MoveStack moves[256], badCaptures[64];
 };