Add relational support to range-op.

Add relational support to range-op.

This patch integrates relations with range-op functionality so that any
known relations can be used to help reduce or resolve ranges.
Initially handle  EQ_EXPR, NE_EXPR, LE_EXPR, LT_EXPR, GT_EXPR and GE_EXPR.

	* range-op.cc (range_operator::wi_fold): Apply relation effect.
	(range_operator::fold_range): Adjust and apply relation effect.
	(*::fold_range): Add relation parameters.
	(*::op1_range): Ditto.
	(*::op2_range): Ditto.
	(range_operator::lhs_op1_relation): New.
	(range_operator::lhs_op2_relation): New.
	(range_operator::op1_op2_relation): New.
	(range_operator::op1_op2_relation_effect): New.
	(relop_early_resolve): New.
	(operator_equal::op1_op2_relation): New.
	(operator_equal::fold_range): Call relop_early_resolve.
	(operator_not_equal::op1_op2_relation): New.
	(operator_not_equal::fold_range): Call relop_early_resolve.
	(operator_lt::op1_op2_relation): New.
	(operator_lt::fold_range): Call relop_early_resolve.
	(operator_le::op1_op2_relation): New.
	(operator_le::fold_range): Call relop_early_resolve.
	(operator_gt::op1_op2_relation): New.
	(operator_gt::fold_range): Call relop_early_resolve.
	(operator_ge::op1_op2_relation): New.
	(operator_ge::fold_range): Call relop_early_resolve.
	* range-op.h (class range_operator): Adjust parameters and methods.