list of unsupported solvers

[redianthus]

I'm creating a single issue instead of having so many.

• STP: https://stp.github.io/
• alt-ergo-free
• monosat: https://github.com/sambayless/monosat (add monosat #554)
• OpenSMT2: https://github.com/usi-verification-and-security/opensmt
• veriT: https://verit.loria.fr/
• Yices: https://github.com/SRI-CSL/yices2 (it has an OCaml API!)

[filipeom]

Yices: https://github.com/SRI-CSL/yices2 (it has an OCaml API!)

I wanted to do this one next because of it. I might give it a shot in a couple days