Use a set to store SearchMoves

We just need to verify if a legal move is among the
SearchMoves, so we don't need a vector for this.

No functional change.

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

src/benchmark.cpp

@@ -19,6 +19,7 @@
 
 #include <fstream>
 #include <iostream>
+#include <set>
 #include <vector>
 
 #include "misc.h"
@@ -121,7 +122,7 @@ void benchmark(int argc, char* argv[]) {
       }
       else
       {
-          Threads.start_thinking(pos, limits, vector<Move>(), false);
+          Threads.start_thinking(pos, limits, set<Move>(), false);
           nodes += RootPosition.nodes_searched();
       }
   }