Import C++11 branch

Import C++11 branch from:

https://github.com/mcostalba/Stockfish/tree/c++11

The version imported is teh last one as of today:
6670e93e50

Branch is fully equivalent with master but syzygy
tablebases that are missing (but will be added with
next commit).

bench: 8080602

src/movegen.cpp

@@ -256,7 +256,7 @@ namespace {
 
   template<Color Us, GenType Type> FORCE_INLINE
   ExtMove* generate_all(const Position& pos, ExtMove* moveList, Bitboard target,
-                        const CheckInfo* ci = NULL) {
+                        const CheckInfo* ci = nullptr) {
 
     const bool Checks = Type == QUIET_CHECKS;