Deferred normal buffer does not preserve negative Z

The Second Life deferred renderer does not preserve negative Z values in the normal buffer.

A side effect of this results in incorrect environment reflections and "light shifting" on certain surfaces where there's a sharp view angle, wherein a view space normal with a negative Z value would be generated.

Test Plan:

• Enable Lighting and Shadows
• Go to the shading testing area in Hippo Hollow
• Go up to the wall with the two lights near it
• Angle your camera so that the wall just to the right side of the screen
• Without the patch, you should notice odd behavior with the lighting seemingly "shifting"
• With the patch, the lighting should stay consistent to the surface