Bindings to external solver, CBC.
CBC is somewhat faster than GLPK, and also has a more permissive licence.
Relies on coin/cbc version 2.8.6.
This package has a few caveats: invalid programs can cause segfaults, and the library-based solver is slower than the command-line based one.
See https://github.com/amosr/limp-cbc for details.