ports-gcc: fix missing header

Index: src/lib/WPXHeader.cpp
--- src/lib/WPXHeader.cpp.orig
+++ src/lib/WPXHeader.cpp
@@ -23,6 +23,8 @@
  * Corel Corporation or Corel Corporation Limited."
  */
 
+#include <string.h>
+
 #include "WPXHeader.h"
 #include "WP3Header.h"
 #include "WP5Header.h"