Core/Log: Readd include of <stdarg.h> to fix compile issues under gcc

(cherry picked from commit d64e6ffade392be32f634b32658a6e0353f369c1)

src/server/shared/Logging/Log.h

@@ -26,6 +26,7 @@
 #include <boost/asio/io_service.hpp>
 #include <boost/asio/strand.hpp>
 
+#include <stdarg.h>
 #include <unordered_map>
 #include <string>
 #include <memory>