  - add code for northern and southern boundaries.   - reorder some loops to save some operations and so that drFBar can be scalar
  - add code for northern and southern boundaries.
  - reorder some loops to save some operations and so that drFBar can be scalar

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