`fctr_ff'
---------

fctr_ff(POLY)
     :: Irreducible univariate factorization over a finite field.

RETURN
     list

POLY
     univariate polynomial over a finite field

   * Defined in `fff'.

   * Factorize POLY into irreducible factors over the current base
     field.

   * The result is a list [[F1,M1],[F2,M2],...], where FI is a monic
     irreducible factor and MI is its multiplicity.

   * The leading coefficient of POLY is abandoned.

     [178] setmod_ff(2^64-95);
     18446744073709551521
     [179]  fctr_ff(x^5+x+1);
     [[1*x+14123390394564558010,1],[1*x+6782485570826905238,1],
     [1*x+15987612182027639793,1],[1*x^2+1*x+1,1]]

References
     *Note `setmod_ff': setmod_ff

