compute gUext,gVext only if diagnostic Um_ext,Vm_ext is on ;  fill those diag. also if momForcing_In_AB=T (was missing).
compute gUext,gVext only if diagnostic Um_ext,Vm_ext is on ;
 fill those diag. also if momForcing_In_AB=T (was missing).

altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h