Include <cstring> in search.h

Now we use memset() directly there.

Spotted by Justin Blanchard.

No functional change.

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

src/search.h

@@ -20,11 +20,12 @@
 #if !defined(SEARCH_H_INCLUDED)
 #define SEARCH_H_INCLUDED
 
+#include <cstring>
+#include <vector>
+
 #include "move.h"
 #include "types.h"
 
-#include <vector>
-
 class Position;
 struct SplitPoint;