Expand list of root-of-volume dotfiles

In addition to `.Spotlight-V100` and `.Trashes`, the following dotfiles
may appear at the root of all OSX volumes (not just external disks):

- `.DocumentRevisions-V100`: auto-save and versions storage
- `.fseventsd`: file system event storage
- `.Temporaryitems`: temp directory used by some applications instead of
                     /tmp and /var/tmp
- `.VolumeIcon.icns`: storage of custom icon for volume, if set