Port NetBSD's UDF implementation

by Oleksandr for FreeBSD

FreeBSD has an implementation of the UDF filesystem but it is not the latest version and doesn't support many features from newer UDF revisions (>=2.01), such as Metadata Partition or Pseudo OverWrite method. Support UDF is also readonly. NetBSD implementation by Reinoud Zandijk supports most of new UDF features and has write support too. First of all I will support new revisions only for reading and subsequently write support.