POSIX Overlay Filesystem (posixovl)

A FUSE (filesystem in userspace) filesystem that provides POSIX
functionality - UNIX-style permissions, ownership, special files -
for filesystems that do not have such, e.g. vfat. It is a modern
equivalent of the UMSDOS fs.

It provides a filesystem view that supports various POSIX operations
while using an otherwise incapable lower filesystem. Filesystems
of various degrees of POSIXness can be utilitzed. VFAT is a
common denominator when it comes to cross-compatibility, though
NTFS -- its features are unused in Linux -- would be another
possibility. Secondly, potent native POSIX-style filesystems can also
be used, though the actual use of doing that remains to be discovered.
