Change all uses of sort() to stable_sort().

src:
	* src/V3Cdc.cpp (CdcVisitor::edgeReport): Change sort to
	stable_sort.
	* src/V3Const.cpp (ConstVisitor::senItemCmp): Likewise.
	* src/V3EmitC.cpp (EmitCImp::emitIntFuncDecls): Likewise.
	* src/V3EmitCSyms.cpp (EmitCSyms::visit(AstNetList*...): Likewise.
	* src/V3GraphAcyc.cpp (GraphAcyc::place): Likewise.
	* src/V3GraphAlg.cpp (V3Graph::sortVertices): Likewise.
	(V3Graph::sortEdges): Likewise.
	* src/V3Order.cpp (OrderVisitor::processEdgeReport): Likewise.