Generate adjusted Rock Ridge attributes, This means that the file ownerships and modes are set to more useful values.  The UID and GID are set to zero, because these are usually only useful on the authors system, and not useful on the client. All the file read bits are set true, so that files and directories are glabbally readable on the client. If any execute bit is set on the file, then set all of the execute bits, so that executables are globally executable on the client. If any search bit is set for a directory, set all the search bits, so that directories are globally searchable by the client. All write bits are cleared. All special mode bits are cleared because file locks are not usefull on a read-only system, and set-id bits are not desirable for uid 0 or gid 0.
