Blender Git Loki

EEVEE: GBuffer: Fix undefined behavior

When evaluating surfaces, the deferred passes needs to sample the
depth buffer. But it also test against the stancil buffer.

Moreover the sampler needs to be a 2D sampler which is not the case
for cubemaps and texture2Darrays.

To overcome this we simply copy the gbuffer depth to another
temp texture using framebuffer blitting.