Warn about using a menu item with wxITEM_CHECK and a bitmap

[KeyWorksRW]

Description:

If a menu item type is set to wxITEM_CHECK and a bitmap is used, the normal checkbox will not be displayed if the item is checked. Instead the bitmap will be shown if checked, and not shown if it is not checked. That might not be what the dev intended, so it would be potentially useful to display a warning about that using our wxInfoBar.

I haven't tested this yet, but I suspect the same problem occurs with wxITEM_RADIO.