netd: Add primitive NAT control

Update: Add stub function to validate interface existance

Signed-off-by: San Mehat <san@google.com>
diff --git a/Android.mk b/Android.mk
index e4a640c..910c819 100644
--- a/Android.mk
+++ b/Android.mk
@@ -16,7 +16,8 @@
                   NetlinkManager.cpp                   \
                   NetlinkHandler.cpp                   \
                   logwrapper.c                         \
-                  TetherController.cpp
+                  TetherController.cpp                 \
+                  NatController.cpp
 
 LOCAL_MODULE:= netd