Function: idealcoprime
Section: number_fields
C-Name: idealcoprime
Prototype: GGG
Help: idealcoprime(nf,x,y): gives an element b in nf such that b. x is an
 integral ideal coprime to the integral ideal y.
Doc: given two integral ideals $x$ and $y$
 in the number field $\var{nf}$, returns a $\beta$ in the field,
 such that $\beta\cdot x$ is an integral ideal coprime to $y$.
