Gnome uses a variant of the "log out" icon for its standard "Exit" icon,
so it should be fine for us to do it too, contrary to what the comment
from back when Tango provider was added in c1d2466a79 (Add wxArtProvider
using Tango icons., 2010-12-31) was saying.
The icons are embedded as PNG images directly in the source code to avoid the
need for installing them. This does make the library larger though so provide
a wxUSE_ARTPROVIDER_TANGO option to turn the new code and associated bloat off.
Also turn it off by default under wxGTK as the native art provider is used
there anyhow.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66505 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
