Function: quadray
Section: number_theoretical
C-Name: quadray
Prototype: GGp
Help: quadray(D,f): relative equation for the ray class field of
 conductor f for the quadratic field of discriminant D (which can also be a
 bnf).
Doc: relative equation for the ray
 class field of conductor $f$ for the quadratic field of discriminant $D$
 using analytic methods. A \kbd{bnf} for $x^2 - D$ is also accepted in place
 of $D$.

 For $D < 0$, uses the $\sigma$ function and Schertz's method.

 For $D>0$, uses Stark's conjecture, and a vector of relative equations may be
 returned. See \tet{bnrstark} for more details.
