Fix wxFont test compilation after wxFont(int flags) ctor removal.

Also mention this incompatible (since 2.9.4) change in the change log.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73889 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775