Install location for nautilus named icon

[Luca Ferretti <elle uca libero it>]

The nautilus icon (the logo) was updated to match the Tango style. You
can see the icon on http://tango.freedesktop.org/Tango_Fridays

We just have a doubt about its location: the system hicolor directory
(${prefix}/share/icons/hicolor/<size>/apps) or the custom nautilus
hicolor directory (${prefix}/share/nautilus/icons/hicolor/<size>/apps)?

This icon will not used in any .desktop file, but only internally in
About dialog[1], so Alex Larsson thinks it should be in custom nautilus
hicolor directory.