HiddenLine Renderer

[Jose' C. <cru...@ce...>]

I've added a draft for a hidden line removal renderer.

It's a multipass OpenGL renderer, and in its current state is more a  
proof of concept than anything.

It registers two renderers, one technical, and another more  
cartoonish, none of them will remain in Quesa in the current state,  
since it's still a work in progress.

We hope they will lite some bulb over your head, and after some more  
drafts and development, we decide which one (or ones) remain as  
renderer in Quesa

with the modifications made to the OpenGL renderer, it's fairly  
simple make fancy things with renderers,

in fact the hiddenline.cpp file is just administrative stuff  
(metahandlers and friends) and almost all the dancing is done inside  
the StartPass methods.