Function: rnfidealhnf
Section: number_fields
C-Name: rnfidealhnf
Prototype: GG
Help: rnfidealhnf(rnf,x): relative version of idealhnf, where rnf is a
 relative numberfield.
Doc: $\var{rnf}$ being a relative number
 field extension $L/K$ as output by \kbd{rnfinit} and $x$ being a relative
 ideal (which can be, as in the absolute case, of many different types,
 including of course elements), computes the HNF pseudo-matrix attached to
 $x$, viewed as a $\Z_K$-module.
