Use one History table per thread

This reduces contention and reduce history trashing
effect especially at high search depths.

No functional change for single CPU case.

After 999 games at 1+0 on Dual Core Intel we have

Mod vs Orig  +233 =526 -240  -2 ELO

We need to test at longer time controls and possibly with
a QUAD where we could foreseen an improvment.

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

src/thread.h

@@ -26,6 +26,7 @@
 //// Includes
 ////
 
+#include "history.h"
 #include "lock.h"
 #include "movepick.h"
 #include "position.h"
@@ -73,6 +74,7 @@ struct Thread {
   volatile bool idle;
   volatile bool workIsWaiting;
   volatile bool printCurrentLine;
+  History H;
   unsigned char pad[64]; // set some distance among local data for each thread
 };