Robert Sachunsky authored Mar 31, 2020 and Edwin Carlinet committed Mar 31, 2020

- avoid using global (header) constants:
  always pass k functionally in internal
  routines
- define macro constants for default k
  at all scales (original 0.2 / 0.3 / 0.5
  scheme)
- use these macro defaults in both API
  (header-defined defaults) and CLIs
  (unit-defined defaults) for all
  variants (sauvola-ms/-fg/-split/-debug)
- in the CLIs, avoid setting the default
  via option parser (which would not be
  distinguishable from an override setting);
  instead, merely hint at the defaults in
  the description string, and also repair
  option priority (defaults < all-k < k2/k3/k4
  override)