[GTK] Do not define *_DEPRECATED macros for the gtk+ stack in preparation of a stable...

[GTK] Do not define *_DEPRECATED macros for the gtk+ stack in preparation of a stable wx release, as we can not
know what functions become deprecated in future releases of gtk+ and co, while the stable wx release should last
the test of time.
We could do some preprocessor magic to automatically define the macros only for development releases (whose minor
version number is odd, not even), but as the releases is close, don't do this at this point, as some compilers
might not like the initial try. I will bring these macros back to HEAD, together with the automation, once 2.8
branches.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@43716 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775