Status: still working on math/sage (See D24195).

Maxima (i.e. ports/math/maxima) is a Lisp application, and our port can use CCL, CMUCL, or SBCL, but to be used by SageMath, ECL is required.

Furthermore, many patches are needed to install a library usable by ECL, and it is closely tied with the version used for ECL.

Since we have to create a special port for lang/ecl-sage (See D24958), it's also safer to recopy math/maxima to math/maxima-sage.