Virtualize fur_source and turn it into a proper API.

Virtualize fur_source and turn it into a proper API.

No more accessing the local info.  Also add fur_source/fold_stmt where ranges
are provided via being specified, or a vector to replace gimple_fold_range.

	* gimple-range-gori.cc (gori_compute::outgoing_edge_range_p): Use a
	fur_stmt source record.
	* gimple-range.cc (fur_source::get_operand): Generic range query.
	(fur_source::get_phi_operand): New.
	(fur_source::register_dependency): New.
	(fur_source::query): New.
	(class fur_edge): New.  Edge source for operands.
	(fur_edge::fur_edge): New.
	(fur_edge::get_operand): New.
	(fur_edge::get_phi_operand): New.
	(fur_edge::query): New.
	(fur_stmt::fur_stmt): New.
	(fur_stmt::get_operand): New.
	(fur_stmt::get_phi_operand): New.
	(fur_stmt::query): New.
	(class fur_depend): New.  Statement source and process dependencies.
	(fur_depend::fur_depend): New.
	(fur_depend::register_dependency): New.
	(class fur_list): New.  List source for operands.
	(fur_list::fur_list): New.
	(fur_list::get_operand): New.
	(fur_list::get_phi_operand): New.
	(fold_range): New.  Instantiate appropriate fur_source class and fold.
	(fold_using_range::range_of_range_op): Use new API.
	(fold_using_range::range_of_address): Ditto.
	(fold_using_range::range_of_phi): Ditto.
	(imple_ranger::fold_range_internal): Use fur_depend class.
	(fold_using_range::range_of_ssa_name_with_loop_info): Use new API.
	* gimple-range.h (class fur_source): Now a base class.
	(class fur_stmt): New.
	(fold_range): New prototypes.
	(fur_source::fur_source): Delete.