Define filesystem attributes with vfs dependency.

Implement udf_rename() using the new genfs_rename() framework.

Fixes PR kern/47986

branches: 1.4.10; 1.4.20; 1.4.24;
Don't generate unused fs_thefs.h headers.

branches: 1.3.14;
Remove all remaining traces of UDF_READWRITE since it has been removed as
option.

branches: 1.2.4;
Import writing part of the UDF file system making optical media like CD's
and DVD's behave like floppy discs. Writing is supported upto and including
version 2.01; version 2.50 and 2.60 will follow.

Also extending the UDF implementation to support symbolic links and
hardlinks.

Added are the mmcformat(8) tool to format rewritable CD/DVD discs and
newfs_udf(8).

Limitations:
all operations can be performed on the file system though the
sheduling is currently optimised for archiving workloads.

mv(1)/rename(2) is currently only implemented for non-directories.

branches: 1.1.4; 1.1.16; 1.1.22; 1.1.72; 1.1.74; 1.1.76; 1.1.78;
Initial import of a UDF file system implementation for NetBSD.

The code supports read access to all media types that CD/DVD type drives
can recognize including DVD-RAM and BD- drives as well as harddisc partions
and vnd devices. UDF versions upto the latest 2.60 are to be supported
though due to lack of test media version 2.50 and 2.60 are not implemented
yet though easy to add. Both open and closed media are supported.

Write access is planned and in preparation. To facilitate this some hooks
are present in the code that are not strictly needed in a read-only
implementation but which allow writing to be added more easily.

Implemented and tested media types are CD-ROM, CD-R, CD-RW, CD-MRW,
DVD-ROM, DVD*R, DVD*RW, DVD+MRW but the same code can also read DVD-RAM,
HD-DVD and BluRay discs. Also vnd devices have been tested with several
sector sizes.

Discs created and written by UDFclient, Nero's InCD and Roxio's
DirectCD/Drag2Disc read fine.