Also, reimplement and re-enable subsumption caching.

gcc/cp/
	* config-lang.in (gtfiles): Add logic.cc.
	* constraint.cc (atomic_constraints_identical_p): Add assertions.
	(hash_atomic_constraint): Likewise.
	(constraints_equivalent_p): New.
	(inchash::add_constraint): New.
	(iterative_hash_constraint): New.
	(decl_constraints): Moved from pt.c.
	(get_constraints): Likewise.
	(set_constraints): Likewise.
	(remove_constraints): Likewise.
	* cp-tree.h (CONSTR_P): New.
	(init_constraint_processing): Remove.
	(constraints_equivalent_p, iterative_hash_constraint): Declare.
	* decl.c (cxx_init_decl_processing): Don't initialize constraints.
	* logic.cc (subsumption_entry): Moved from pt.c.
	(subsumption_hasher): Likewise.
	(subsumption_cache): Likewise.
	(lookup_subsumption): Likewise.
	(save_subsumption): Likewise.
	(subsumes_constraints_nonnull): Use subsumption cache.
	* pt.c: Move aforementioned declarations out of this file.
	(init_constraint_processing): Remove.

From-SVN: r277407