* Rename solver_scope for fixplex tests
(otherwise the wrong constructor is called for polysat's solver_scope)
* Update conflict_core
* simplify
* Be clearer about constraint_literal lifetime
* remove old comment
* Remove status (positive/negative) from constraint
* Use constraint_literal in the solver
* Fix build (constraint -> get_constraint)
* Add macro to disable linear solver for development
* Move new_* and add_* to header
* Add ref_vector_core::push_back(ref<T>&&)
* Attempt to simplify lifetime handling
* Make operator bool() explicit
* clause improvements
* display boolean assignment
* clause::resolve
* bug fixes
* more fixes
* final case of backtrack
* Rename to neg_cond
* Add some logging utilities
* Implement case of forbidden interval covering the whole domain
* Implement diseq_narrow
* Do not activate constraint if we are in a conflict state
* comments
* Assert that lemma isn't undefined
* Update revert_decision to work in the case where narrowing causes propagation
* Fix case of non-disjunctive lemma from forbidden intervals
* Conflict should not leak outside user scope
* Add guard to decide(), some notes
* Add test case
* Add constraints to watchlist of unassigned variable during propagation
* Move common propagation functionality into base class
* Combine eq/diseq narrow
* Compute forbidden interval for equality constraints by considering them as p <=u 0 (or p >u 0 for disequalities)
