Function: hyperellextremalmodels
Section: elliptic_curves
C-Name: hyperellextremalmodels
Prototype: GG
Help: hyperellextremalmodels(C,p): C being a hyperelliptic curve given by an
 integral Weierstrass equation, compute a maximal chain of minimal Weierstrass
 models at p. Return a vector [n, V] where n is the length of the chain of
 minimal Weierstrass models at p, and V is vector of length 1 or 2 containing
 the extremal models of the chain.
Doc:
 $C$ being a hyperelliptic curve given by an integral Weierstrass equation,
 compute a maximal chain of minimal Weierstrass models at the prime number $p$.
 Return a vector $[n, V]$ where $n$ is the length of the chain of minimal
 Weierstrass models at $p$, and $V$ is vector of length $1$ or $2$ containing the
 extremal models of the chain.
