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.

src/qt/window.cpp

@@ -650,10 +650,12 @@ void wxWindowQt::ScrollWindow( int dx, int dy, const wxRect *rect )
 }
 
 
+#if wxUSE_DRAG_AND_DROP
 void wxWindowQt::SetDropTarget( wxDropTarget * WXUNUSED( dropTarget ) )
 {
     wxMISSING_IMPLEMENTATION( __FUNCTION__ );
 }
+#endif
 
 void wxWindowQt::SetWindowStyleFlag( long style )
 {