Fix several build errors in WXQT

Move declaration of wxOwnerDrawnBase::ms_defaultMargin to correct file.
Do not include headers when wxUSE_UIACTIONSIMULATOR is disabled.
Add guards for wxUSE_DRAG_AND_DROP.
Use a different wxFont constructor in printing sample, which is also available in WXQT.

include/wx/qt/window.h

@@ -133,7 +133,9 @@ public:
 
     QWidget *GetHandle() const wxOVERRIDE;
 
+#if wxUSE_DRAG_AND_DROP
     virtual void SetDropTarget( wxDropTarget *dropTarget ) wxOVERRIDE;
+#endif
 
 #if wxUSE_ACCEL
     // accelerators