Function: elljacobi
Section: transcendental
C-Name: elljacobi
Prototype: GGp
Help: elljacobi(z,k): returns the vector of the three Jacobi elliptic functions
 [sn(z,k),cn(z,k),dn(z,k)].
Doc: returns $[\text{sn}(z,k), \text{cn}(z,k), \text{dn}(z,k)]$,
 where \text{sn}, \text{cn} and \text{dn} are the three Jacobi elliptic
 functions.
