Remove duplicated control names strings declarations from wxOSX.

Remove duplicated control names strings declarations from wxOSX.

There is no need to declare wxFooNameStr constants in wx/osx/foo.h files as
they are already declared in wx/foo.h.

Also remove a couple of header/forward declarations unnecessary for the same
reason.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66993 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775