testing/lcalc: new aport

Michael Rubinstein's L-function calculator https://gitlab.com/sagemath/lcalc

Needed for #14155

I get this warnings and I don't know what should I do with them

libtool: warning: remember to run 'libtool --finish /usr/lib'
libtool: warning: '../../src/libLfunction/libLfunction.la' has not been installed in '/usr/lib'