analyzer: use unique_ptr for rejected_constraint

analyzer: use unique_ptr for rejected_constraint

gcc/analyzer/ChangeLog:
	* diagnostic-manager.cc (process_worklist_item): Use
	std::unique_ptr rather than plain rejected_constraint *.
	* engine.cc (exploded_path::feasible_p): Likewise.
	(feasibility_state::maybe_update_for_edge): Likewise.
	* exploded-graph.h (feasibility_problem::feasibility_problem):
	Likewise.
	(feasibility_problem::~feasibility_problem): Delete.
	(feasibility_problem::m_rc): Use std::unique_ptr.
	(feasibility_state::maybe_update_for_edge): Likewise.
	* feasible-graph.cc (feasible_graph::add_feasibility_problem):
	Likewise.
	* feasible-graph.h (class infeasible_node): Likewise.
	(feasible_graph::add_feasibility_problem): Likewise.
	* region-model.cc (region_model::add_constraint): Likewise.
	(region_model::maybe_update_for_edge): Likewise.
	(region_model::apply_constraints_for_gcond): Likewise.
	(region_model::apply_constraints_for_gswitch): Likewise.
	(region_model::apply_constraints_for_exception): Likewise.
	* region-model.h (class region_model): Likewise for decls.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>