Function: matfrobenius
Section: linear_algebra
C-Name: matfrobenius
Prototype: GD0,L,Dn
Help: matfrobenius(M,{flag},{v=x}): Return the Frobenius form of the square
 matrix M. If flag is 1, return only the elementary divisors as a vector of
 polynomials in the variable v. If flag is 2, return a two-components vector
 [F,B] where F is the Frobenius form and B is the basis change so that
 M=B^-1*F*B.

