Fixes to wxFont strike-through support in wxOSX.

Don't create strike-through fonts by default.

Also add support for strike-through in wxCarbon.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77695 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775