"Octave" namespace for Octave C++ sources for 3.2?

[John W. Eaton]

On  6-Aug-2008, Michael Goffioul wrote:

| I'm just asking because I was thinking about the graphics code and
| the possibility to remove some graphics_ prefixes as well. For instance,
| turn graphics_backend class into octave::graphics::backend.

I think a change like that would be OK.  Should we consider defining
any other nested namespaces?

jwe