Cycles: Anisotropic BSDF enabled, with tangents now computed from the active UV map.

It's using the Ward BSDF currently, which has some energy loss so might be a bit
dark. More/better BSDF options can be implemented later.

Patch by Mike Farnsworth, some modifications by me. Currently it's not possible yet
to set a custom tangent, that will follow as part of per-bsdf normals patch.

intern/cycles/render/graph.cpp

@@ -468,6 +468,12 @@ void ShaderGraph::default_inputs(bool do_osl)
 
 					connect(geom->output("Position"), input);
 				}
+				else if(input->default_value == ShaderInput::TANGENT) {
+					if(!geom)
+						geom = new GeometryNode();
+
+					connect(geom->output("Tangent"), input);
+				}
 			}
 		}
 	}