Remove private wxDisclosureTriangle control.

Remove the private and undocumented control and it's usage in wxGenericCollapsiblePane. The class used a low resolution bitmap which looks bad on high resolution displays. The generic implementation using wxRendererNative::DrawCollapseButton() is better fit even on OS X.

src/osx/button_osx.cpp

@@ -138,57 +138,3 @@ wxSize wxButtonBase::GetDefaultSize()
 {
     return wxAnyButton::GetDefaultSize();
 }
-
-//-------------------------------------------------------
-// wxDisclosureTriangle
-//-------------------------------------------------------
-
-bool wxDisclosureTriangle::Create(wxWindow *parent, wxWindowID id, const wxString& label,
-   const wxPoint& pos, const wxSize& size, long style,const wxValidator& validator, const wxString& name )
-{    
-    DontCreatePeer();
-    if ( !wxControl::Create(parent, id, pos, size, style, validator, name) )
-        return false;
-
-    SetPeer(wxWidgetImpl::CreateDisclosureTriangle(this, parent, id, label, pos, size, style, GetExtraStyle() ));
-
-    MacPostControlCreate( pos, size );
-    // passing the text in the param doesn't seem to work, so let's do it again
-    SetLabel( label );
-
-    return true;
-}
-
-void wxDisclosureTriangle::SetOpen( bool open )
-{
-    GetPeer()->SetValue( open ? 1 : 0 );
-}
-
-bool wxDisclosureTriangle::IsOpen() const
-{
-   return GetPeer()->GetValue() == 1;
-}
-
-bool wxDisclosureTriangle::OSXHandleClicked( double WXUNUSED(timestampsec) )
-{
-    // Just emit button event for now
-    wxCommandEvent event(wxEVT_BUTTON, m_windowId);
-    event.SetEventObject(this);
-    ProcessCommand(event);
-
-    return true;
-}
-
-wxSize wxDisclosureTriangle::DoGetBestSize() const
-{
-    wxSize size = wxWindow::DoGetBestSize();
-
-    // under Carbon the base class GetBestSize() implementation doesn't seem to
-    // take the label into account at all, correct for it here
-#if wxOSX_USE_CARBON
-    size.x += GetTextExtent(GetLabel()).x;
-#endif // wxOSX_USE_CARBON
-
-    return size;
-}
-