Function: bnrstark
Section: number_fields
C-Name: bnrstark
Prototype: GDGp
Help: bnrstark(bnr,{subgroup}): bnr being as output by
 bnrinit(,,1), finds a relative equation for the class field corresponding to
 the module in bnr and the given congruence subgroup (the trivial subgroup if
 omitted) using Stark's units. The ground field and the class field must be
 totally real.

