[Goptical] Code and manual update

[Alexandre Becoulet]

Hi list,

A new version of the Goptical source tree is hosted on a mercurial 
repository:

  http://hg.savannah.gnu.org/hgweb/goptical/

Here is a list of major source code changes:
 - Rendering classes in Io namespace have been rewritten.
 - Io:RendererX11 and Io::RendererX3d class have been added.
 - Material::Abbe model glass material class has been added.
 - Sys::SourceRays component has been added.
 - Sys::Stop component has been added.
 - Sys::Lens component can now handle a list of optical surfaces.
 - The project has been split in 2 libraries located in the 
goptical_core and goptical_design sub-packages.
 - Many code fixes and API cleanup has been done.
 - Some tests have been written.

More examples are now available and described in the tutorial section of 
the updated manual:

  http://www.gnu.org/software/goptical/manual/Tutorial.html

--
Alexandre