Try to prefetch as soon as position key is ready

Move prefetching code inside do_move() so to allow a
very early prefetching and to put as many instructions
as possible between prefetching and following retrieve().

With this patch retrieve() times are cutted of another 25%

No functional change.

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

src/position.h

@@ -98,6 +98,7 @@ struct StateInfo {
   StateInfo* previous;
 };
 
+class TranspositionTable;
 
 /// The position data structure. A position consists of the following data:
 ///
@@ -258,6 +259,7 @@ public:
   void undo_move(Move m);
   void do_null_move(StateInfo& st);
   void undo_null_move();
+  void setTranspositionTable(TranspositionTable* tt);
 
   // Static exchange evaluation
   int see(Square from, Square to) const;
@@ -356,6 +358,7 @@ private:
   File initialKFile, initialKRFile, initialQRFile;
   StateInfo startState;
   StateInfo* st;
+  TranspositionTable* TT;
 
   // Static variables
   static int castleRightsMask[64];