Abstract tracing routines into a class.

Generalize range tracing into a class and integrae it with gimple_ranger.
Remove the old derived trace_ranger class.

	* Makefile.in (OBJS): Add gimple-range-trace.o.
	* gimple-range-cache.h (enable_new_values): Remove unused prototype.
	* gimple-range-fold.cc: Adjust headers.
	* gimple-range-trace.cc: New.
	* gimple-range-trace.h: New.
	* gimple-range.cc (gimple_ranger::gimple_ranger): Enable tracer.
	(gimple_ranger::range_of_expr): Add tracing.
	(gimple_ranger::range_on_entry): Ditto.
	(gimple_ranger::range_on_exit): Ditto.
	(gimple_ranger::range_on_edge): Ditto.
	(gimple_ranger::fold_range_internal): Ditto.
	(gimple_ranger::dump_bb): Do not calculate edge range twice.
	(trace_ranger::*): Remove.
	(enable_ranger): Never create a trace_ranger.
	(debug_seed_ranger): Move to gimple-range-trace.cc.
	(dump_ranger): Ditto.
	(debug_ranger): Ditto.
	* gimple-range.h: Include gimple-range-trace.h.
	(range_on_entry, range_on_exit): No longer virtual.
	(class trace_ranger): Remove.
	(DEBUG_RANGE_CACHE): Move to gimple-range-trace.h.