message: fix machine_topology PCI bus ID buffer overflow
  found by a compiler warning for snprintf
diff: @@ -249,7 +249,7 @@ void MachineTopology::load_objects(
  hwloc_obj_type_snprintf(ances_type, sizeof(ances_type), ancestor, 0);
  vector.back().ancestor_type = std::string(ances_type);
  // Write the PCI Bus ID from the object info.
  - char pci_bus_id[13];
  + char pci_bus_id[14];
  snprintf(pci_bus_id, sizeof(pci_bus_id), "%04x:%02x:%02x.%01x",
  obj->attr->pcidev.domain, obj->attr->pcidev.bus,
  obj->attr->pcidev.dev, obj->attr->pcidev.func);
  