add some missing includes to allow compiling with gcc 4.3 (patch by Bircoph)

src/config.cpp

@@ -20,6 +20,7 @@
 
 #include <algorithm>
 #include <sstream>
+#include <string.h>
 #include "config.hpp"
 #include "gettext.hpp"
 #include "log.hpp"

src/network.cpp

@@ -37,6 +37,7 @@
 #include <ctime>
 
 #include <signal.h>
+#include <string.h>
 #if defined(_WIN32) || defined(__WIN32__) || defined (WIN32)
 #undef INADDR_ANY
 #undef INADDR_BROADCAST

src/sdl_utils.cpp

@@ -24,6 +24,7 @@
 #include "video.hpp"
 
 #include <algorithm>
+#include <string.h>
 #include <cassert>
 #include <cmath>
 #include <iostream>