Properly set GORI relation trios.

Properly set GORI relation trios.

When relation trios were added to GORI, there was only one use.  As they are
utilized more by range-ops, it is apparent that the implelemtation was
not complete.  This patch fleshes it out completely so that every GORI
operation has a complete relation trio.

	* gimple-range-gori.cc (gori_compute::compute_operand_range): Do
	not abort calculations if there is a valid relation available.
	(gori_compute::refine_using_relation): Pass correct relation trio.
	(gori_compute::compute_operand1_range): Create trio and use it.
	(gori_compute::compute_operand2_range): Ditto.
	* range-op.cc (operator_plus::op1_range): Use correct trio member.
	(operator_minus::op1_range): Use correct trio member.
	* value-relation.cc (value_relation::create_trio): New.
	* value-relation.h (value_relation::create_trio): New prototype.