Forbid creation of wxPaintEvent objects from user code

This doesn't work anyhow, so it's better to prevent the code doing this
from compiling instead of getting run-time asserts or worse.

Also simplify construction of these events inside wxWidgets by passing
the window itself to the ctor instead of passing just its ID and calling
SetEventObject() separately later.

For consistency, do the same thing for wxNcPaintEvent too.

interface/wx/event.h

@@ -2222,7 +2222,7 @@ public:
         need a window to be repainted, use wxWindow::Refresh() instead of
         trying to manually create an event of this class.
     */
-    wxPaintEvent(int id = 0);
+    explicit wxPaintEvent(wxWindow* window);
 };