pub type PFN_glCombinerOutputNV = unsafe extern "system" fn(_stage: GLenum, _portion: GLenum, _abOutput: GLenum, _cdOutput: GLenum, _sumOutput: GLenum, _scale: GLenum, _bias: GLenum, _abDotProduct: GLboolean, _cdDotProduct: GLboolean, _muxSum: GLboolean);