+Eliminate fluxes%KPP_salt_flux

  Eliminated the KPP_salt_flux element of the forcing type, which is no longer
being used after the revisions to pseudo_salt_tracer_column_physics.  Also moved
5 allocatable arrays (KPP_NLTheat, KPP_NLTscalar, KPP_buoy_flux, KPP_temp_flux
and KPP_salt_flux) out of diabatic_CS, replacing them with ordinary arrays in
diabatic_ALE(), diabatic_ALE_legacy() and layered_diabatic().  This change could
reduce the high-water memory footprint of the model when KPP is in use.  All
answers are bitwise identical, but one element of a publicly visible type has
been eliminated.

src/core/MOM_forcing_type.F90

@@ -126,9 +126,8 @@ module MOM_forcing_type
   real, pointer, dimension(:,:) :: &
     netMassIn     => NULL(), & !< Sum of water mass fluxes into the ocean integrated over a
                                !! forcing timestep [H ~> m or kg m-2]
-    netMassOut    => NULL(), & !< Net water mass flux out of the ocean integrated over a forcing timestep,
+    netMassOut    => NULL()    !< Net water mass flux out of the ocean integrated over a forcing timestep,
                                !! with negative values for water leaving the ocean [H ~> m or kg m-2]
-    KPP_salt_flux => NULL()    !< KPP effective salt flux [ppt m s-1]
 
   ! heat associated with water crossing ocean surface
   real, pointer, dimension(:,:) :: &