Function: rnfisfree
Section: number_fields
C-Name: rnfisfree
Prototype: lGG
Help: rnfisfree(bnf,M): given a bnf attached to a number field K and a
 projective Z_K module M given by a pseudo-matrix, return true (1) if M
 is free else return false (0).
Doc: given a $\var{bnf}$ attached to a number field $K$ and
 a projective $\Z_{K}$-module $M$ given by a pseudo-matrix, return true (1) if
 $M$ is free else return false (0). If $M$ is a polynomial with coefficients
 in $K$, replace it by the pseudo-matrix returned by \kbd{rnfpseudobasis}.
