Remove value_range_equiv.

Remove value_range_equiv.

With legacy VRP gone, value_range_equiv serves no purpose and any uses
of it can just be replaced with value_range.

gcc/ChangeLog:

	* Makefile.in: Remove value-range-equiv.o
	* gimple-array-bounds.cc
	(array_bounds_checker::array_bounds_checker): Remove comment.
	* tree-vrp.cc (supported_types_p): Remove use of value_range_equiv.
	* value-query.cc (class equiv_allocator): Same.
	(range_query::allocate_value_range_equiv): Remove.
	(range_query::free_value_range_equiv): Remove.
	(range_query::get_value_range): Remove.
	* value-query.h (class range_query): Remove get_value_range.
	Remove allocate_value_range_equiv.
	Remove free_value_range_equiv.
	* vr-values.cc (compare_ranges): Replace value_range_equiv with
	value_range.
	(simplify_using_ranges::get_vr_for_comparison): Same.
	(simplify_using_ranges::compare_names): Same.
	* vr-values.h: Remove value_range_equiv references.
	* value-range-equiv.cc: Removed.
	* value-range-equiv.h: Removed.