Fix regression of commit b2802021acf8aa9b363ebef383c8dc8c8079ffa4 (Bug 711): varying in/out mapping is different in vertex/fragment shader!

Vertex shader:   varying -> out
Fragemnt shader: varying -> in

NV GLSL compiler ignored in/out direction,
where ATI GLSL compiler failed (could not find gcu_Weight, due to dead code).