VS2019 seems to complain if std::string is used but <string> is not actually #included.

src/quit_confirmation.hpp

@@ -18,6 +18,7 @@ class CVideo;
 
 #include <cassert>
 #include <vector>
+#include <string>
 
 #include "utils/functional.hpp"
 

src/synced_commands.hpp

@@ -16,6 +16,7 @@
 
 #include <map>
 #include <exception>
+#include <string>
 
 #include "utils/functional.hpp"