Function: hyperellauto
Section: elliptic_curves
C-Name: hyperellauto
Prototype: GDG
Help: hyperellauto(E,{nf}): C being a hyperelliptic curve given by a Weierstrass
 equation, either over the rationals or over the number field nf if given,
 return the group of automorphisms of C as a vector of changes of
 coordinates of the form [e, [a,b;c,d], H].
Doc:
 $C$ being a hyperelliptic curve given by a Weierstrass equation,
 either over the rationals or over the number field \var{nf} if given,
 return the group of automorphisms of $C$ as a vector of changes of coordinates
 of the form $[e, [a,b;c,d], H]$.

 $C$ can be given either by a squarefree polynomial $P$ such that
 $C: y^{2} = P(x)$ or by a vector $[P,Q]$ such that
 $C: y^{2} + Q(x)\*y = P(x)$ and $Q^{2}+4\*P$ is squarefree.
