Lots of small code clean-up

Removed the following:

1. use statement for a type that is not used in the module
2. return statement inside a function that doesn't need to be there
3. comment refering to a block of code that was removed earlier in this
   development

Also cleaned up one last comment that refered to surface flux output instead of
output for the GCM.

src/marbl_interface_public_types.F90

@@ -498,10 +498,10 @@ end subroutine marbl_single_output_constructor
   subroutine marbl_output_add(this, num_elements, field_name, output_id,            &
                               marbl_status_log, num_levels)
 
-  ! MARBL uses pointers to create an extensible allocatable array. The surface
-  ! forcing output fields (part of the intent(out) of this routine) are stored
-  ! in this%outputs_for_GCM(:). To allow the size of this%outputs_for_GCM to
-  ! grow, the process for adding a new field is:
+  ! MARBL uses pointers to create an extensible allocatable array. The output
+  ! fields (part of the intent(out) of this routine) are stored in
+  ! this%outputs_for_GCM(:). To allow the size of this%outputs_for_GCM to grow,
+  ! the process for adding a new field is:
   !
   ! 1) allocate new_output to be size N (one element larger than this%outputs_for_GCM)
   ! 2) copy this%outputs_for_GCM into first N-1 elements of new_output

src/marbl_interior_tendency_mod.F90

@@ -35,7 +35,6 @@ module marbl_interior_tendency_mod
   use marbl_interface_public_types, only : marbl_domain_type
   use marbl_interface_public_types, only : marbl_forcing_fields_type
   use marbl_interface_public_types, only : marbl_saved_state_type
-  use marbl_interface_public_types, only : marbl_output_for_GCM_type
   use marbl_interface_public_types, only : marbl_running_mean_0d_type
 
   use marbl_logging, only : marbl_log_type
@@ -323,10 +322,6 @@ subroutine marbl_interior_tendency_compute( &
     call setup_local_tracers(kmt, marbl_tracer_indices, tracers(:,:), autotroph_local, &
          tracer_local(:,:), zooplankton_local, totalChl_local)
 
-    !-----------------------------------------------------------------------
-    !  Store total chlorophyll if requested by GCM
-    !-----------------------------------------------------------------------
-
     call set_surface_particulate_terms(surface_flux_forcing_indices, POC, POP, P_CaCO3, &
          P_CaCO3_ALT_CO2, P_SiO2, dust, P_iron, QA_dust_def(:), dust_flux_in)
 
@@ -3836,7 +3831,6 @@ subroutine check_forcing(forcings, forcing_indices, marbl_status_log)
         write(log_message, "(A, E11.3, A)") "Total column fractions sum to ", col_frac_sum, &
                                             ", which is not close to 1"
         call marbl_status_log%log_warning(log_message, subname)
-        return
       end if
     end if