Function: nfisisom
Section: number_fields
C-Name: nfisisom
Prototype: GG
Help: nfisisom(x,y): as nfisincl but tests whether x is isomorphic to y.
Doc: as \tet{nfisincl}, but tests for isomorphism. If either $x$ or $y$ is a
 number field, a much faster algorithm will be used.
