Initial value-relation code.

Initial value-relation code.

This code provides a both an equivalence and relation oracle which can be
accessed via a range_query object.  This initial code drop includes the
oracles and access them, but does not utilize them yet.

	* Makefile.in (OBJS): Add value-relation.o.
	* gimple-range.h: Adjust include files.
	* tree-data-ref.c: Adjust include file order.
	* value-query.cc (range_query::get_value_range): Default to no oracle.
	(range_query::query_relation): New.
	(range_query::query_relation): New.
	* value-query.h (class range_query): Adjust.
	* value-relation.cc: New.
	* value-relation.h: New.