SH-1618 FIX -- Lighting and shadows crash ATI macs

* Fixed ATI mac "lighting and shadows" related crash
* Fixed up numerous GL errors on macs related to multiple color formats,
  the use of glEnable/glDisable on textures above the texture unit count
  and old ATI-specific code that was not appropriate for Mac.
* Disabled SSAO for ATI macs due to it not working with shadows
* Ongoing work to properly get shadows and SSAO functioning on ATI macs is required.

Reviewed by davep