Function: quadhilbert
Section: number_theoretical
C-Name: quadhilbert
Prototype: GDGp
Help: quadhilbert(D,{pq}): relative equation for the Hilbert class field
 of the quadratic field of discriminant D (which can also be a bnf).
 If D<0, pq (if supplied) is a 2-component vector [p,q], where p,q are the
 prime numbers needed for Schertz's method. In that case, return 0 if [p,q]
 not suitable.

