Introduce req_vec_is_impossible_to_fulfill()
Introduce the new functions req_is_impossible_to_fulfill() and req_vec_is_impossible_to_fulfill(). They check if a requirement or requirement vector is known to be impossible to fulfill in the current ruleset.
Introduce the new functions req_is_impossible_to_fulfill() and req_vec_is_impossible_to_fulfill(). They check if a requirement or requirement vector is known to be impossible to fulfill in the current ruleset.