Add warning for joint WLS.
Add warning for joint WLS.

JuKa87/OpenMx,jpritikin/OpenMx,jpritikin/OpenMx,mhunter1/OpenMx,mhunter1/OpenMx,mhunter1/OpenMx,JuKa87/OpenMx,jpritikin/OpenMx,jpritikin/OpenMx,mhunter1/OpenMx,JuKa87/OpenMx,jpritikin/OpenMx,JuKa87/OpenMx,jpritikin/OpenMx,mhunter1/OpenMx,JuKa87/OpenMx,JuKa87/OpenMx,mhunter1/OpenMx