feat(opensmt/egraph/EgraphStore): subst x * x with x^2
fix(realpaver_rp_interval): (-oo, 0] * (-oo, oo) = (-oo, oo)
fix(realpaver/rp_operator_sat): memory leak
feat(realpaver/rp_operator): show constraint when debugging
fix(realpaver/rp_interval): display_simple outputs to stderr
tests(realpaver): add realpaver tests using Google Test