The idea is that only one thread opens listen socket and runs accept().
Other threads emulate listen()/accept() by waiting for connected
socket from the main thread. Main thread distributes connected sockets
according to round robin pattern. Patch introduce new specialization
for server_socket_impl and network_stack: posix_ap_server_socket_impl
and posix_ap_network_stack respectively. _ap_ stand for auxiliary processor.
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