Function: rnfbasistoalg
Section: number_fields
C-Name: rnfbasistoalg
Prototype: GG
Help: rnfbasistoalg(rnf,x): relative version of nfbasistoalg, where rnf is a
 relative numberfield.
Doc: computes the representation of $x$
 as a polmod with polmods coefficients. Here, $\var{rnf}$ is a relative number
 field extension $L/K$ as output by \kbd{rnfinit}, and $x$ an element of
 $L$ expressed on the relative integral basis.
