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Fourier transform matrix in Galois field   dm = dftmtx(alph)
dm = dftmtx(alph) returns a Galois array that represents the
discrete Fourier transform operation on a Galois vector, with
respect to the Galois scalar alph. The element alph is a
primitive nth root of unity in the Galois field GF(2m) =
GF(n+1); that is, n must be the smallest positive value of k for
which alph^k equals 1. The discrete Fourier transform has size n
and dm is an n-by-n array. The array dm represents the transform
in the sense that dm times any length-n Galois column vector
yields the transform of that vector.      Note:   The inverse
discrete Fourier transform matrix is dftmtx(1/alph).   The
example below illustrates the discrete Fourier transform and its
inverse, with respect to the element gf(3,4). The example
examines the first n powers of that element to make sure that
only the nth power equals one. Afterward, the example transforms
a random Galois vector, undoes th