Update fog technique from plane based to radial

[ghost]

Fog Technique

Source 2007 fog seems to be implemented based on a plane based fog technique versus a more modern radially fog technique. As a result the viewer will be able to see further into the fog along the edges. Furthermore, the fog is rotation dependent. Something that appears under fog at one view may change if the player rotates slightly.

Just an example on zs_obj_vertigo_v25.

[VCSoldier]

Bumping this now that HL2 has offical radial fog support