Hello,

The following patch adds Symmetrica 2.0. It builds, but I have a few
questions and remarks:

- I added the package in "sagemath.scm" because its main use would be
  with Sage, and it is already heavily patched by Sage. Should I move it
  to "algebra.scm" or "maths.scm"?

- The package creates a static library, because that is what Sage seems
  to expect (see <https://git.sagemath.org/sage.git/plain/build/pkgs/symmetrica/patches/makefile>).

- I'm not sure about the installation. Headers go into
  "%out/include/symmetrica" and static library into "%out/lib". Is that
  right?

Regards,

-- 
Nicolas Goaziou