Use Ok/Cancel dialog instead of Yes/No one in CheckFit().

Use Ok/Cancel dialog instead of Yes/No one in CheckFit().

This has the advantage of being able to close the dialog with "Esc" and also allows us to not specify the label for the "Cancel" button at all and use the default one, which is especially important under MSW where the label returned by wxGetStockLabel(wxID_CANCEL) is actually not the same string as is used in the native message boxes (they don't define an accelerator for the cancel button).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@61524 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775