Default RenderState DepthFunc to RS_CMP_GREATER_EQUAL, makes shaders without a RenderState set default to it
https://files.facepunch.com/sam/1b0711b1/tt3.png
Readjust depth bias on debug shaders for reverse depth
Fix shadow in reversed depth
https://files.facepunch.com/sam/1b0711b1/tt2.png