digits hilbert_inverse.adb accuracy test
 200-digit floating point, Hilbert vs random matrix
for N by N matrices, N=2, 4, 8, 16, 32, 64, 128, 256
(this may hit storage limitations)

N= 2, norm= 0.00000000000000E+00, mindiag= 1.00000000000000E+20
     avgerr= 1.00000000000000E-200, maxerr= 2.00000000000000E-200
random  norm= 0.00000000000000E+00, mindiag= 1.00000000000000E+20
     avgerr= 5.00000000000000E-201, maxerr= 1.00000000000000E-200

N= 4, norm= 0.00000000000000E+00, mindiag= 1.00000000000000E+20
     avgerr= 4.81250000000000E-198, maxerr= 1.20000000000000E-197
random  norm= 0.00000000000000E+00, mindiag= 1.00000000000000E+20
     avgerr= 3.93750000000000E-201, maxerr= 2.50000000000000E-200

N= 8, norm= 0.00000000000000E+00, mindiag= 1.00000000000000E+20
     avgerr= 4.19080937500000E-192, maxerr= 5.26730000000000E-191
random  norm= 0.00000000000000E+00, mindiag= 1.00000000000000E+20
     avgerr= 1.04276562500000E-200, maxerr= 5.26000000000000E-200

N= 16, norm= 0.00000000000000E+00, mindiag= 1.00000000000000E+20
     avgerr= 5.12187622887715E-180, maxerr= 3.93901199856600E-179
random  norm= 0.00000000000000E+00, mindiag= 1.00000000000000E+20
     avgerr= 1.14902343750000E-199, maxerr= 2.12000000000000E-198

N= 32, norm= 0.00000000000000E+00, mindiag= 1.00000000000000E+20
     avgerr= 7.99500435996704E-157, maxerr= 2.77134420219856E-155
random  norm= 0.00000000000000E+00, mindiag= 1.00000000000000E+20
     avgerr= 2.11127880859375E-200, maxerr= 7.95620000000000E-199