Fixes Issue #157 (Router segfaults) (#159)

Found a number of problems with the router when compiling on linux

* Expected malloc()'ed memory to be zeroed resulting in segfault
* IPC_NOWAIT in iplayer loop means incoming traffic will be delayed until outgoing traffic is received.
* When configured with two BIP interfaces, broadcast loops ensue because the broacast traffic is not correctly filtered.  I think the safest thing to do here is to use the SO_BINDTODEVICE setsockopt.

apps/router/msgqueue.h

@@ -82,7 +82,8 @@ bool send_to_msgbox(
 /* returns received message */
 BACMSG *recv_from_msgbox(
     MSGBOX_ID src,
-    BACMSG * msg);
+    BACMSG * msg,
+    int flags);
 
 void del_msgbox(
     MSGBOX_ID msgboxid);