PIObject::deleteLater important fix

PIWaitEvent::sleep() method
PITimer thread imp wait optimization, migrate to interruptable sleeps

libs/main/core/piwaitevent_p.h

@@ -31,7 +31,7 @@
 #endif
 
 
-class PIWaitEvent {
+class PIP_EXPORT PIWaitEvent {
 public:
 	~PIWaitEvent();
 
@@ -44,6 +44,7 @@ public:
 	void create();
 	void destroy();
 	bool wait(int fd = -1, CheckRole role = CheckRead);
+	bool sleep(int us); // return if sleep done
 	void interrupt();
 	bool isCreate() const;
 	void * getEvent() const; // WINDOWS only