Because we are also going to use it to check continuity of dates
across slices.

We need it to open `e_overestim.txt`. unit was undefined for `i_slice
/=  - 1`. The bug came from commit af5da9e8.

We also change the rule on the input value of `n_dates`. Before we could
have a finite value of `n_dates` if there was a single slice. Now if
we want a finite value of `n_dates` then we have to specify a slice,
even if there is only one. This seems clearer.

It will change if the user chooses a slice.

Because we are going to introduce the choice of a slice in the namelist.

I do not remember why I chose to write to standard error. First it is
clearer to write only error messages to standard error. Second the
order of messages on standard error coming from the Fortran code and
from the shapelib C library does not seem deterministic, and this is
annoying to compare runs.

Remove dummy argument `max_delta` of procedure `dispatch_snapshot`,
use module variable instead.

Remove dummy arguments nlon, nlat, periodic, `dist_lim` of
procedure `overlap`, use module variables instead.

Remove dummy arguments nlon, nlat, corner, step, copy, `max_delta` of
procedure `get_snapshot`, use module variables instead.

Which read namelists. Motivations: diminish the number of arguments of
procedure overlap; lighten the main program unit. We conditionally
compile MPI calls in `read_grid` because we want to use variables of
module`read_grid_m` in procedure `read_snapshot`, and `read_snapshot`
is called from sequential program `test_nearby_extr`.

Remove procedure `write_aux`. Write to `ishape_last.txt` in procedure
`write_snapshot` and write `grid_nml` in procedure `input_ssh`. In
`input_ssh`, if `grid_nml.txt` already exists, check consistency with
input NetCDF files. Downgrade dummy arguments `corner_deg` and
`step_deg` of `input_ssh` to local variables. Read and write
`grid_nml` at SHPC level, only one file for both orientations and all
slices.

Assume that a slice is in a directory
"{shpc_dir}/{orientation}/Slice_{slice}" where shpc_dir can be any
name, orientation is "Anticyclones" or "Cyclones" and slice is an
integer. Do not read or create any longer a file "orientation.txt" in
the slice directory. Add procedure `get_slice_dir`. Add dummy
arguments cyclone and slice to procedure `shpc_open`. Add dummy
argument slice to procedure `shpc_create`.

Split derived type `shpc_slice_handler` into `shpc_slice_handler` and
`shpc_slice_meta out`. Do not mix what is necessary to open, create
and close, analogous to a logical unit, with what comes from reading
the files.

Create component `unit` for `ishape_last.txt` in derived type
`shpc_slice_handler`. Open, create and close `ishape_last.txt` at the
same time we open, create and close the shapefiles. So we use
`read_opcol` instead of `read_column` when we need to read
`ishape_last.txt`.

We are more clearly separating opening files and reading from them.

Use `e_overestim.txt` instead of `node_id_param.json`. Since commit
43d2eff6, we wrote only `e_overestim` to the JSon file. Simpler to
write the value alone in a text file.

Since `NR_util` has been integrated into Jumble.

Just sparing one test on rank.

But reading from them is not here yet.

Since `shpc_open` is called by all processes, reading d0 and
`ishape_last` in `shpc_open` implies that we do not broadcast d0 and
`ishape_last`.

Since processes need d0 to allocate `ishape_last`.

Store `ishape_last` and first date in components of derived type
shpc. We then remove arguments `d_init` and `ishape_last` of procedures
`read_snapshot` and `get_snapshot`.

Preparing for the case of several input SHPC.

It was confusing to mix opening an SHPC with broadcasting some part of
the resulting shpc variable.

In procedure `get_snapshot`.

Note that we then have to declare `d_init` before `ishape_last` in
procedure `get_snapshot`.