Interim backward-compatible fixes for wxmac 3.0.1 for OS X 10.10

This includes all of the change sets from the upstream wxwidgets project that
correctly build for 10.10, as well as 10.9 (and earlier.) These changes are
currently accepted in the upstream trunk, but will not be available until the
next release is cut (which will probably be a non-trivial amount of time after
10.10 releases.)

References:
http://trac.wxwidgets.org/ticket/16329
http://trac.wxwidgets.org/changeset/76744
http://trac.wxwidgets.org/changeset/76743

(Note - The original patch attached to ticket #16329 above should be ignored.)