Added universal locking mechanism which will solve problems

Added universal locking mechanism which will solve problems
with protocols wanting to use the same port on the same interface
during reconfiguration time.

How to use locks: In the if_notify hook, just order locks for the
interfaces you want to work with and do the real socket opening after the
lock hook function gets called. When you stop using the socket, close
it and rfree() the lock.

Please update your protocols to use the new locking mechanism.