Never clear stats

Based on an idea and patch by VoyagerOne.

Small simplification, but was tedted for an ELO gain anyway.

STC:
LLR: 2.95 (-2.94,2.94) [-1.00,4.00]
Total: 5375 W: 1119 L: 977 D: 3279

LTC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 17893 W: 2984 L: 2792 D: 12117

bench 8322847

src/movepick.h

@@ -21,7 +21,6 @@
 #define MOVEPICK_H_INCLUDED
 
 #include <algorithm> // For std::max
-#include <cstring>   // For std::memset
 
 #include "movegen.h"
 #include "position.h"
@@ -44,7 +43,6 @@ struct Stats {
 
   const T* operator[](Piece pc) const { return table[pc]; }
   T* operator[](Piece pc) { return table[pc]; }
-  void clear() { std::memset(table, 0, sizeof(table)); }
 
   void update(Piece pc, Square to, Move m) {
 

src/search.cpp

@@ -339,10 +339,6 @@ namespace {
     beta = VALUE_INFINITE;
 
     TT.new_search();
-    History.clear();
-    CounterMovesHistory.clear();
-    Gains.clear();
-    Countermoves.clear();
 
     size_t multiPV = Options["MultiPV"];
     Skill skill(Options["Skill Level"]);