Only write `used_config_nml.txt` and `grid_nml.txt` if `leave_trace`.

Promote u and v to variables of module `input_ssh_m`, and remove them
as dummy arguments of `input_ssh`, `set_contours`, `mean_speed` and
`set_max_speed`. u and v are defined in procedure `input_ssh` and used
only in procedure `mean_speed`.

Remove dummy argument corner of function `mean_speed`, not used any
longer.

The case of u and v is different from the case of ssh. For ssh, we
want to restrict as much as possible the size of the array we work
with because we search all the contours in the corresponding
window. But for u and v, we only do a bilinear interpolation, without
a call to locate or hunt within the interpolation procedure, so there
is nothing to be gained to work on only a window of u and
v. Furthermore, we are preparing to allow staggering of the u and v
grid with respect to the ssh grid so if we wanted a window of u and v,
there would be the complication of choosing the window taking the
staggering into account.

It was not convenient to read them with input function or on the
command line: too much to read this way, and not clear when saved in
JSON text file. And we already had to create a namelist file
anyway. And this way the namelists can be extended transparently.

Pass a namelist object instead of a string to functions
`loop_inst_eddies` and `process_1_file`. Preparing to integrate the
date and the slice to this object.

Read `inst_eddies_nml.txt` out of function
`loop_inst_eddies`. Preparing to modify the date in the namelist in
`inst_eddies_Aviso.py`.

Instead of `config_nml.txt`. Preparing to include other namelists in
this file.

Bug fix: do not provide standard input for `inst_eddies_Aviso.py`, it
does not read it.

In the case of non-uniform longitude-latitude grid: we read the whole
coordinate arrays from the NetCDF file; we have a different way of
inverting the projection, in `invert_proj`; the program `eddy_graph`
does not use `corner_whole` and step, which are not defined, it uses
instead the shapefile `extr_proj`.

In `extr_map.nc`.

Preparing for a non-uniform longitude latitude grid.

For a non-uniform longitude-latitude grid. As in `input_ssh` for
`max_radius(1)`. See commit 803b9bcc.

Preparing to make dummy arguments longitude and latitude optional.

Rename variable `corner` of module `read_grid_m` to `corner_whole`. As
in module `input_ssh_m`. Cf. commit ef43e372.

Rather than calling dbffileisnull or shpfileisnull. This should be
faster and more robust.

Of derived type `shpc_slice_handler`.

Since it is already written to a shapefile.

Always write shapefile `extr_proj` in procedure
`save_snapshot`. `save_snapshot` is only used in tests. In these
tests, `read_snapshot` is called so `extr_proj` is computed. We want
to check as much as possible with `save_snapshot`.

Rather than the value of `s%list(1)%extr%coord_proj(1)`.

Preparing to generalize to a non-uniform longitude-latitude grid.