- ddierckx is a 'real*8' version of dierckx
  generated by Pearu Peterson <pearu@ioc.ee>.
- dierckx (in netlib) is fitpack by P. Dierckx

LOCAL EDIT, 2026-08-01. Twelve files differ from the upstream sources:

    curfit percur parcur clocur concur regrid
    parsur pogrid spgrid sphere surfit polar

Each set `tol` and `maxit` as locals and passed them to its `fp*` worker.
Both are now trailing dummy arguments, inserted immediately before `ier`,
so `scijit.interpolate.fitters` can reach them. The two local assignments
are gone; each file carries a comment in their place recording the original
values. Nothing else changed, and no `fp*` worker signature changed.

The original values are NOT the same number in all twelve. `curfit.f` wrote
`tol = 0.1d-02`; the other eleven wrote `tol = 0.1e-02`, which is a default
REAL literal in fixed form and reaches `real*8 tol` as the widened float32
(1.00000004749745131E-03 against 1.00000000000000002E-03). The glue resolves
its `tol=-1.0` sentinel to whichever literal the routine's own source held,
so an unchanged call is an unchanged computation.
