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/core/piincludes.h

@@ -44,6 +44,7 @@ class PIInit;
 #endif
 class PIChar;
 class PICout;
+class PIWaitEvent;
 
 struct lconv;