Fix missing outputs
A number of piglits fail because of errors like
error: fragment shader input `vso_g1' has no matching output in the previous stage
error: fragment shader input `vso_g3' has no matching output in the previous stage
e.g. "glsl-routing".
This patch fixes this by emitting blank outputs for non-matching outputs. The values are not initialized, so results may be undefined.
Edited by Gert Wollny