Move VREL values to their own enumerated type.

Move VREL values to their own enumerated type.

Re-using some common things like EQ_EXPR and other relationals made
certain things easier, but complicated debugging and added extra overhead
when accessing lookup tables.   With forthcoming additional relation types,
it makes more sense to simple have a distinct relation kind.

	* gimple-range-fold.cc (fold_using_range::range_of_phi): Use new VREL_*
	enumerated values.
	* gimple-range-path.cc (maybe_register_phi_relation): Ditto.
	* range-op.cc (*::lhs_op1_relation): Return relation_kind, and use
	new VREL enumerated values.
	(*::lhs_op2_relation): Ditto.
	(*::op1_op2_relation): Ditto.
	(*::fold_range): Use new VREL enumerated values.
	(minus_op1_op2_relation_effect): Ditto.
	(range_relational_tests): Ditto.
	* range-op.h (fold_range, op1_range, op2_range): Use VREL_VARYING.
	(lhs_op1_relation, lhs_op2_relation, op1_op2_relation): Return
	relation_kind.
	(*_op1_op2_relation): Return relation_kind.
	(relop_early_resolve): Use VREL_UNDEFINED.
	* value-query.cc (range_query::query_relation): Use VREL_VARYING.
	* value-relation.cc (VREL_LAST): Change enumerated value.
	(vrel_range_assert): Delete.
	(print_relation): Remove range assert.
	(rr_negate_table): Adjust table to use new enumerated values..
	(relation_negate): Remove range assert.
	(rr_swap_table): Adjust.
	(relation_swap): Remove range assert.
	(rr_intersect_table): Adjust.
	(relation_intersect): Remove range assert.
	(rr_union_table): Adjust.
	(relation_union): Remove range assert.
	(rr_transitive_table): Adjust.
	(relation_transitive): Remove range assert.
	(equiv_oracle::query_relation): Use new VREL enumerated values.
	(equiv_oracle::register_relation): Ditto.
	(relation_oracle::register_stmt): Ditto.
	(dom_oracle::set_one_relation): Ditto.
	(dom_oracle::register_transitives): Ditto.
	(dom_oracle::query_relation): Ditto.
	(path_oracle::register_relation): Ditto.
	(path_oracle::query_relation): Ditto.
	* value-relation.h (enum relation_kind_t): New relation_kind.
	(*_op1_op2_relation): Adjust prototypes.