improve vectorization of layers_fluxcalc.F, step 1  - split loops, make TatU/V 2D arrays. This along reduces the cpu time spent    in this routine by more than a factor of 3 on an NEC-SX8
improve vectorization of layers_fluxcalc.F, step 1
 - split loops, make TatU/V 2D arrays. This along reduces the cpu time spent
   in this routine by more than a factor of 3 on an NEC-SX8

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