fixes for

make[2]: Entering directory `/home/laotse/src/abs/zeromq-git/src/libzmq-build/src'
  CXX    libzmq_la-address.lo
address.cpp: In destructor 'zmq::address_t::~address_t()':
address.cpp:41:29: error: deleting object of polymorphic class type 'zmq::tcp_address_t' which has non-virtual destructor might cause undefined behaviour [-Werror=delete-non-virtual-dtor]
cc1plus: all warnings being treated as errors

src/tcp_address.hpp

@@ -40,7 +40,7 @@ namespace zmq
 
         tcp_address_t ();
         tcp_address_t (const sockaddr *sa, socklen_t sa_len);
-        ~tcp_address_t ();
+        virtual ~tcp_address_t ();
 
         //  This function translates textual TCP address into an address
         //  strcuture. If 'local' is true, names are resolved as local interface