Add missing include headers for compilation on x86 targets.

Change-Id: I99f7b79bfb5b6305a0772f418a54ace50cac1bbe
diff --git a/NatController.cpp b/NatController.cpp
index 8c88698..28f1fe2 100644
--- a/NatController.cpp
+++ b/NatController.cpp
@@ -21,6 +21,7 @@
 #include <fcntl.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
+#include <string.h>
 
 #define LOG_TAG "NatController"
 #include <cutils/log.h>