migrate to async IO model

new PIIODevice::interrupt() virtual method
new PIWaitEvent private class
PIEthernet and PISerial basically tested on Windows and Linux

libs/main/cloud/picloudclient.h

@@ -43,6 +43,7 @@ public:
 	void setKeepConnection(bool on);
 	bool isConnected() const {return is_connected;}
 	ssize_t bytesAvailable() const override {return buff.size();}
+	void interrupt() override;
 
 	EVENT(connected);
 	EVENT(disconnected);