Elliptic function support




Here is a replacement for maxima's ellipt.lisp.  The current version
basically just numerically evaluates some of the elliptic functions.
The key changes:

o The elliptic functions sn(u|m), cn(u|m), dn(u|m) are defined.
  Maxima knows about some special values of these and knows how to
  differentiate wrt to the first parameter.  When given numerical
  args, Maxima will compute the value.
o The inverse functions asn, acn, and adn are defined.  Maxima knows
  how to evaluate these and find the derivative wrt to the first
  parameter. 
o The elliptic functions F(phi|m) and E(phi|m) are defined.  Maxima
  knows about some special values, and and compute them when given
  numerical args.  Maxima knows how to differentiate them.

Missing things:
o Maxima doesn't know how to compute the integrals of the elliptic
  functions, even though they're easily defined in terms of other
  elliptic functions.

I think I got them defined correctly, but some bugs may still exist.
There are a lot of changes, so no diff is given.

Hope this is useful to someone,

Ray

Attached file: ellipt.lisp