This compiler doesn't exist any more and was probably unsupported even in 2.8,
let alone 2.9, so remove all the __MWERKS__ tests to simplify things.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71102 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775