* Simplify adding lemmas
* Remove misleading constructor from tmp_assign.
The idea is that tmp_assign is only created on the stack and
short-lived. Instead of having a convenience constructor that takes a
constraint_ref, it's clearer to have an explicit .get() at the call
site.
* Remove some log messages
* bugfix
* fix
* Add stub for conflict_core
* wip
* Add example by Clemens
* 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
* Add polysat logging support
* Don't really need the usual log levels
* Indent log headings
* Add display method to ptr_vector
* Add some logging to solver
* Use __FUNCSIG__ on MSVC
