[Code clean] Unused value

[sbryngelson]

The following is the output from looking for -Wunused-value appending to the GNU compile options. Not all of these have to be resolved, and some shouldn't be because they are required, but many are problematic.

   26 |     integer, private :: err_code, ierr !<
      |                                1
Warning: Unused PRIVATE module variable 'err_code' declared at (1) [-Wunused-value]
[46/62] Building Fortran object CMakeFiles/pre_process.dir/src/common/m_compile_specific.f90.o
[47/62] Building Fortran object CMakeFiles/pre_process.dir/fypp/pre_process/m_helper.fpp.f90.o
/Users/henryleberre/dev/MFC/src/common/m_helper.fpp:307:13:
--

  130 | 
      |                                                        1
Warning: Unused PRIVATE module variable 'res' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/common/m_variables_conversion.fpp:1213:57:

 1213 |         real(kind(0d0)), dimension(num_fluids) :: alpha_K
--

    7 |     integer, private :: col(7) = [ &
      |                              1
Warning: Unused PRIVATE module variable 'col' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_nvtx.f90:13:43:

   13 |     character(len=256), private :: tempName
      |                                           1
Warning: Unused PRIVATE module variable 'tempname' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_nvtx.f90:59:42:

   59 |         type(nvtxEventAttributes) :: event
--

  140 | 
      |                                1
Warning: Unused PRIVATE module variable 'err_code' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_mpi_proxy.fpp:2052:36:

 2052 |         integer :: pack_offsets(1:3), unpack_offsets(1:3)
--

   30 |     real(kind(0d0)) :: length_x, length_y, length_z
      |                                                   1
Warning: Unused PRIVATE module variable 'length_z' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_compute_levelset.fpp:31:29:

   31 |     real(kind(0d0)) :: radius
      |                             1
Warning: Unused PRIVATE module variable 'radius' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_compute_levelset.fpp:33:35:

   33 |     type(bounds_info) :: x_boundary, y_boundary, z_boundary  !<
      |                                   1
Warning: Unused PRIVATE module variable 'x_boundary' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_compute_levelset.fpp:33:47:

   33 |     type(bounds_info) :: x_boundary, y_boundary, z_boundary  !<
      |                                               1
Warning: Unused PRIVATE module variable 'y_boundary' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_compute_levelset.fpp:33:59:

   33 |     type(bounds_info) :: x_boundary, y_boundary, z_boundary  !<
      |                                                           1
Warning: Unused PRIVATE module variable 'z_boundary' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_compute_levelset.fpp:29:57:

   29 |     real(kind(0d0)) :: x_centroid, y_centroid, z_centroid
      |                                                         1
Warning: Unused PRIVATE module variable 'z_centroid' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_compute_levelset.fpp:391:39:

  391 |         real(kind(0d0)) :: radius, dist
--

  301 | 
      |                           1
Warning: Unused PRIVATE module variable 'test' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_weno.fpp:1041:20:

 1041 |         integer :: i, j
--

  185 |                 is2%beg:is2%end, &
      |                        1
Warning: Unused PRIVATE module variable 'c' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_cbc.fpp:98:60:

   98 |     ! CBC Coefficients =========================================================
      |                                                            1
Warning: Unused PRIVATE module variable 'f_rs_vf' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_cbc.fpp:98:73:

   98 |     ! CBC Coefficients =========================================================
      |                                                                         1
Warning: Unused PRIVATE module variable 'f_src_rs_vf' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_cbc.fpp:186:39:

  186 |                 is3%beg:is3%end, 1:adv_idx%end))
      |                                       1
Warning: Unused PRIVATE module variable 're' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_cbc.fpp:1304:32:

 1304 |                               ix, iy, iz)
--

  134 |         ! Generating file header for a new run-time information file
      |                               1
Warning: Unused PRIVATE module variable 'ccfl_max' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_data_output.fpp:119:63:

  119 |             !! Creation date of the run-time information file
      |                                                               1
Warning: Unused PRIVATE module variable 'ccfl_sf' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_data_output.fpp:1701:20:

 1701 |         integer :: i !< Generic loop iterator
--

  106 |     type(scalar_field), allocatable, dimension(:) :: grad_x_vf, grad_y_vf, grad_z_vf, norm_vf
      |                                                              1
Warning: Unused PRIVATE module variable 'grad_x_vf' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_start_up.fpp:106:73:

  106 |     type(scalar_field), allocatable, dimension(:) :: grad_x_vf, grad_y_vf, grad_z_vf, norm_vf
      |                                                                         1
Warning: Unused PRIVATE module variable 'grad_y_vf' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_start_up.fpp:106:84:

  106 |     type(scalar_field), allocatable, dimension(:) :: grad_x_vf, grad_y_vf, grad_z_vf, norm_vf
      |                                                                                    1
Warning: Unused PRIVATE module variable 'grad_z_vf' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_start_up.fpp:106:93:

  106 |     type(scalar_field), allocatable, dimension(:) :: grad_x_vf, grad_y_vf, grad_z_vf, norm_vf
      |                                                                                             1
Warning: Unused PRIVATE module variable 'norm_vf' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/simulation/m_start_up.fpp:1314:23:

 1314 |         integer :: ierr
--

   46 |     integer, private :: err_code, ierr
      |                                1
Warning: Unused PRIVATE module variable 'err_code' declared at (1) [-Wunused-value]
[39/48] Building Fortran object CMakeFiles/post_process.dir/src/common/m_compile_specific.f90.o
[40/48] Building Fortran object CMakeFiles/post_process.dir/src/post_process/m_checker.f90.o
[41/48] Building Fortran object CMakeFiles/post_process.dir/fypp/post_process/m_data_output.fpp.f90.o
--
[42/48] Building Fortran object CMakeFiles/post_process.dir/fypp/post_process/m_variables_conversion.fpp.f90.o
/Users/henryleberre/dev/MFC/build/staging/9ea585db54/include/post_process/case.fpp:124:56:

Warning: Unused PRIVATE module variable 'res' declared at (1) [-Wunused-value]
/Users/henryleberre/dev/MFC/src/common/m_variables_conversion.fpp:1213:57:

 1213 |         real(kind(0d0)), dimension(num_fluids) :: alpha_K