games/crack-attack: unbreak build with Clang 6 (C++14 by default)

libc++ doesn't like "using namespace std" in C++11

Communicator.cxx:139:73: error: invalid operands to binary expression ('__bind<int &, sockaddr *, unsigned long>' and 'int')

if (bind(connection_socket, (sockaddr *) &address, sizeof(address)) < 0) {
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~

Reported by: pkg-fallout
Approved by: portmgr blanket