Fix missing header for ports-gcc
Index: src/resource.cxx
--- src/resource.cxx.orig
+++ src/resource.cxx
@@ -19,6 +19,7 @@
 // (See the included file COPYING / GPL-2.0)
 //
 
+#include <string.h>
 #include "resource.h"
 #include "blackboxstyle.h"