Add some headers needed for MSVC.

Reisiger spotted and tested the fix.

src/serialization/parser.hpp

@@ -21,6 +21,7 @@
 #include "global.hpp"
 
 #include <iosfwd>
+#include <string>
 
 class config;
 class t_string;

src/server/user_handler.cpp

@@ -16,6 +16,8 @@
 
 #include "mail.hpp"
 
+#include <ctime>
+
 bool user_handler::send_mail(const std::string& to_user,
 		const std::string& subject, const std::string& message) {