Moved stable tool tip concept into the BToolManager class.

* This removes the fVisibleToolTip member from BView, and fixes bug #5669;
  BToolTipManager::ShowTip() now gets the owner of the tool tip as an extra
  parameter.
* Removed the work-around to hide that bug.
* Improved ToolTipTest application to include more test cases like a view that
  periodically update its tool tip via SetToolTip(const char*), and one that
  sets a new tool tip every second.
* Furthermore, added a test that shows that inner views inherit the tool tip
  of their parents.
* Fixed another bug in BToolTipManager::ShowTip() that would release an
  extra reference to the tool tip currently shown.

headers/private/interface/ToolTipManager.h

@@ -18,7 +18,8 @@ class BToolTipManager {
 public:
 	static	BToolTipManager*	Manager();
 
-			void				ShowTip(BToolTip* tip, BPoint point);
+			void				ShowTip(BToolTip* tip, BPoint point,
+									void* owner);
 			void				HideTip();
 
 			void				SetShowDelay(bigtime_t time);