High-precision accuracy measurements

The scripts in this directory measure the relative error of libcerf
functions against ball-arithmetic references (python-flint / Arb). The
figures quoted in the ACCURACY sections of the man pages come from them:

  wofz_relerr.py             w_of_z at the generated test points and at random
                             points beyond |z| = 7
  cheb_relerr_testpoints.py  erfcx, im_w_of_x, voigt_hwhm at their generated
                             test points, split by code path
  cheb_relerr_random.py      the same at random points over wide ranges
  voigt_hwhm_large_ratio.py  voigt_hwhm for gamma/sigma between 1e3 and 1e8
  wofz_components.py         re_w_of_z and im_w_of_z close to the two axes,
                             where the modulus criterion does not bind (#29)
  wofz_near_axis.py          the expansion of Re w about the real axis used by
                             w_of_z: recurrence, order, and its limit (#29, #30)

Requirements: python3 with python-flint; the library under test, found
through LIBCERF_PATH or the system library search; the test tables in
../../test and the reference modules in ../ppapp. Each script prints the
maxima it finds; its docstring says which man-page figures depend on it.

The broader statistics of the w_of_z page (10^9 random points inside
|z| < 7, 3e9 beyond) come from ttapp modes e and H; see the cgt
manuscript and its data directory.
