Track Unity shaders

Anyone can downloaded these from the Unity website.
Fix Unity Internal-PrePassLighting.shader for Stereo 3D

NOTE: Pixel shader fix needs to be tested. Turns out Dreamfall uses a
different variation of this shader (though World of Diving appears to
use this one).
Add remaining lighting shaders extracted from Dreamfall Chapters
Dreamfall Chapters: Fix remaining light shaders (untested!)

This is a pre-emptive fix - I haven't verified any of these.