Support to read/write NFSv4 named attributes

[lionelconswork]

Hi Ronnie,

We've been working with the libnfs client for Windows and need to read/write NFS named attributes, because the commercial Windows NFSv4 clients (Exceed, Hummingbird, OpenText) store Windows streams (ADS) in these attributes.

NFSv4 server support is not a problem, Solaris 11 and FreeBSD 15 support NFS named attributes.

Thanks for the help!

[lionelconswork]

ms-nfs41-client also supports Windows streams via NFS named attributes (https://sourceforge.net/p/ms-nfs41-client/mailman/message/59285184/).