New opengl rendering breaks some stuff

[smcameron]

Just recording this here so these things don't fall off the map and to make it clear that these are known issues.

Some rendering modes don't work anymore after commit bbd7409

• flat shading with wireframe outline
• wireframe with black_tris
• bright line wireframe
• dotted lines in a liine mesh
• nav trident isn't colored by depth
• Derelict objects show up as gray silhouettes (probably due
  to incorrect normals, mesh_derelict() needs attention, and new
  code for computing vertex normals and coplanar triangles for meshes
  outside the context of reading meshes from stl files needs to be
  written.
• Skybox is broken

[smcameron]

Derelicts and asteroid shading is now partially fixed by giving them all vertex normals that are just copied from the triangle face normals, but it's still not doing the co-planar face stuff, nor the adaptive vertex normal stuff.

[jv4779]

Wireframe with black tris and skybox are now working.

I think flat shading with wireframe and brightline wireframe will end up as "will not fix".

[smcameron]

Fine by me. I only originally had that mode because it was trivially easy in the software renderer to combine wireframe and flat shading, not because it was something that was needed for anything.

[smcameron]

I think we got most of this either sorted out, or replaced by something better.