Work in progress on better ordering for comb loops:

src:
	* V3Graph.cpp (V3graph::debug): Make sensitive to source file.
	* V3GraphAcyc.cpp (GraphAcyc::debug): Likewise.
	* V3graphAlg.cpp (GraphAlgSubtrees::followEdge): Created.
	(GraphAlgSubtrees::vertexIterateAll): Make cut edges show.
	* V3Order.cpp (WhichVertex): Make WV_SETL dependent on
	NEW_ORDERING.
	(OrderUser::newVarUserVertex): Likewise.
	(OrderVisitor::m_settleVxp): Make dependent on NEW_ORDERING.
	(OrderVisitor::visit (AstNodeVarRef*, AstNuser*)): Reorder logic
	for clarity.
	(OrderVisitor::OrderVisitor): Make m_settleVxp initialization
	dependent on NEW_ORDERING.
	(OrderVisitor::processEdgeReport): Make test for STL dependent on
	NEW_ORDERING.
	* V3OrderGraph.h (OrderSettleVertex): Make declaration dependent
	on NEW_ORDERING.
	(OrderChangeDetEdge): Likewise.

test_regress:
	* t/t_unoptflat_simple.v: Add --report-unoptflat option.