Remove value_query, push into sub&fold class

	* tree-ssa-propagate.cc (substitute_and_fold_engine::value_on_edge):
	Move from value-query.cc.
	(substitute_and_fold_engine::value_of_stmt): Ditto.
	(substitute_and_fold_engine::range_of_expr): New.
	* tree-ssa-propagate.h (substitute_and_fold_engine): Inherit from
	range_query.  New prototypes.
	* value-query.cc (value_query::value_on_edge): Relocate.
	(value_query::value_of_stmt): Ditto.
	* value-query.h (class value_query): Remove.
	(class range_query): Remove base class.  Adjust prototypes.