Added selectable TCP_WRITE_FLAG_COPY mode on a per-socket basis, updated lwIP driver for socket limit checks

src/picoTCP.cpp

@@ -744,7 +744,7 @@ namespace ZeroTier {
 	int picoTCP::pico_Socket(struct pico_socket **p, int socket_family, int socket_type, int protocol)
 	{
 		int err = 0;
-		if(!can_provision_new_socket()) {
+		if(!can_provision_new_socket(socket_type)) {
 			DEBUG_ERROR("cannot create additional socket, see PICO_MAX_TIMERS. current=%d", pico_ntimers());
 			errno = EMFILE;
 			err = -1;