Function: rnfhnfbasis
Section: number_fields
C-Name: rnfhnfbasis
Prototype: GG
Help: rnfhnfbasis(bnf,M): given a bnf attached to a number field K and a
 projective Z_K module M given by a pseudo-matrix, returns either a true
 HNF basis of M if one exists, or zero otherwise. If M is a polynomial with
 coefficients in K, replace it by the pseudo-matrix returned by
 rnfpseudobasis.
Doc: given a \var{bnf} attached to a number field $K$ and a projective
 $\Z_{K}$-module $M$ given by a pseudo-matrix, returns either a true HNF basis
 of $M$ if one exists, or zero otherwise. If $M$ is a polynomial with
 coefficients in $K$, replace it by the pseudo-matrix returned by
 \kbd{rnfpseudobasis}.

