[Proj] Jacobi + Guyou projection; conformal map of ellipsoid to sphere

[Charles Karney]

I've updated my notes on Jacobi's conformal projection of a triaxial
ellipsoid; see

   http://geographiclib.sourceforge.net/1.41/jacobi.html

New stuff:

* the limits, ellipsoid of revolution and sphere, are easily obtained;

* the Guyou projection (and hence the Peirce quincuncial projection) are
   special cases of Jacobi's projection (which predates both of these);

* Jacobi + Guyou can be used to map a triaxial ellipsoid conformally
   onto a sphere.

   --Charles