Add GORI tracing faciltiies.

Debugging range-ops and gori unwinding needed some help.

	* gimple-range-gori.cc (gori_compute::gori_compute): Enable tracing.
	(gori_compute::compute_operand_range): Add tracing.
	(gori_compute::logical_combine): Ditto.
	(gori_compute::compute_logical_operands): Ditto.
	(gori_compute::compute_operand1_range): Ditto.
	(gori_compute::compute_operand2_range): Ditto.
	(gori_compute::outgoing_edge_range_p): Ditto.
	* gimple-range-gori.h (class gori_compute): Add range_tracer.