neercs: some refactoring.

src/gpu/shader.cpp

@@ -519,8 +519,6 @@ void Shader::SetUniform(ShaderUniform const &uni, mat4 const &m)
 
 void Shader::SetTexture(ShaderUniform const &uni, int id, int index)
 {
-    if (id == -1)
-        return;
 #if defined USE_D3D9 || defined _XBOX
     /* FIXME: unimplemented */
 #elif !defined __CELLOS_LV2__