This sub-package provides a generic FFT API for multiplication of
polynomials over GF(2), and an implementation of Cantor's algorithm.

Three different FFT types are defined. They define similar interfaces. In
the documentation below, XXX may be one of
    gf2x_fake_fft -- just a proxy implementation that actually calls the
                     normal multiplication operations. Don't use, as it
                     incurs extra copies.
    gf2x_cantor_fft -- use Cantor's additive FFT
    gf2x_ternary_fft -- use Schönhage's ternary FFT

Other FFT modules can conceivably be added.

The actual documentation of the api can be found in the template.h
(pseudo-) header.