netfs utils

[Ludovic Courtès]

BTW, mboxfs contains a set of generic simple operations on a netfs filesystem,
such as creating a node, creating a link to another node without having to
worry about computing the path of the target node (see fsutils.[ch]).

I think this kind of tool should be part of libnetfs (I believe it cannot go
into libfshelp since it is netfs-specific) for instance, and there should be
an equivalent in libdiskfs too.

Thanks,
Ludovic.