Fix protocol probe. Will detect ADC and TLS handshake - any other request

will simply cause the hub to close the connection.
Fix problems with write events not being processed due to a read event taking presendence.
Fix bug #86: Windows does not have "getrlimit()".

src/tools/adcrush.c

@@ -337,6 +337,7 @@ void runloop(size_t clients)
 	{
 		ADC_client_destroy(client[n]);
 		free(client[n]);
+		client[n] = 0;
 	}
 }