Function: nfbasis
Section: number_fields
C-Name: nfbasis0
Prototype: GD0,L,DG
Help: nfbasis(x,{flag=0},{p}): integral basis of the field Q[a], where a is
 a root of the polynomial x, using the round 4 algorithm. Second and third
 args are optional. Binary digits of flag mean 1: assume that no square of a
 prime>primelimit divides the discriminant of x, 2: use round 2 algorithm
 instead. If present, p provides the matrix of a partial factorization of the
 discriminant of x, useful if one wants only an order maximal at certain
 primes only

