Add eval cache infrastructure

With this patch series we want to introduce a per-thread
evaluation cache to store node evaluation and do not
rely anymore on the TT table for this.

This patch just introduces the infrastructure.

No functional change.

src/thread.h

@@ -22,6 +22,7 @@
 
 #include <vector>
 
+#include "evaluate.h"
 #include "material.h"
 #include "movepick.h"
 #include "pawns.h"
@@ -108,6 +109,7 @@ public:
   void wait_for_stop_or_ponderhit();
 
   SplitPoint splitPoints[MAX_SPLITPOINTS_PER_THREAD];
+  Eval::Table evalTable;
   MaterialTable materialTable;
   PawnTable pawnTable;
   size_t idx;