MYST3: TinyGL Renderer

This PR contains an implementation of the software renderer that runs for the engine Myst3.
The renderer shows pretty much the same result as the openGL one, except for the resolution of textures.
ie. tinyGL doesn't support textures larger than 256x256.
Calling tglBlendFunc a second time here looks like a mistake. You can test additive blending by loading this savegame http://q22mv7t0jl.piecejointe.net/ and looking inside the flower.