Enable mouse tracking on construction of every wxQt widget

Not all controls use wxWindow::Create(), so move setMouseTracking() call
where it is always executed.

Closes https://github.com/wxWidgets/wxWidgets/pull/1528

src/qt/window.cpp

@@ -319,8 +319,6 @@ bool wxWindowQt::Create( wxWindowQt * parent, wxWindowID id, const wxPoint & pos
             m_qtWindow = new wxQtWidget( parent, this );
     }
 
-
-    GetHandle()->setMouseTracking(true);
     if ( !wxWindowBase::CreateBase( parent, id, pos, size, style, wxDefaultValidator, name ))
         return false;