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.

include/wx/event.h

@@ -2337,12 +2337,14 @@ private:
 
 class WXDLLIMPEXP_CORE wxPaintEvent : public wxEvent
 {
+    // This ctor is only intended to be used by wxWidgets itself, so it's
+    // intentionally declared as private when not building the library itself.
+#ifdef WXBUILDING
 public:
-    wxPaintEvent(int Id = 0)
-        : wxEvent(Id, wxEVT_PAINT)
-    {
-    }
+#endif // WXBUILDING
+    explicit wxPaintEvent(wxWindowBase* window = NULL);
 
+public:
     // default copy ctor and dtor are fine
 
     virtual wxEvent *Clone() const wxOVERRIDE { return new wxPaintEvent(*this); }
@@ -2353,11 +2355,14 @@ private:
 
 class WXDLLIMPEXP_CORE wxNcPaintEvent : public wxEvent
 {
+    // This ctor is only intended to be used by wxWidgets itself, so it's
+    // intentionally declared as private when not building the library itself.
+#ifdef WXBUILDING
 public:
-    wxNcPaintEvent(int winid = 0)
-        : wxEvent(winid, wxEVT_NC_PAINT)
-        { }
+#endif // WXBUILDING
+    explicit wxNcPaintEvent(wxWindowBase* window = NULL);
 
+public:
     virtual wxEvent *Clone() const wxOVERRIDE { return new wxNcPaintEvent(*this); }
 
 private: