sftp server submodule for OpenSSH

 Green End SFTP Server is an SFTP server supporting up to protocol
 version 6. It is possible to use it as a drop-in replacement for the
 OpenSSH server (which supports only protocol version 3).
 .
  * Protocol versions 3 and higher:
    * Upload and download files
    * List files
    * Create directories and symbolic links
    * Rename and delete files
  * Protocol versions 4 and higher:
    * Filename encoding translation
    * Text mode transfers
    * String owner/group names (instead of numeric)
    * Sub-second timestamps (where supported by server OS)
  * Protocol versions 5 and higher:
    * Extended rename semantics (e.g. atomic overwrite)
  * Protocol versions 6 and higher:
    * Create hard links
  * Several SFTP extensions
 .
 Features of SFTP protocol versions are listed more detailed at
 <http://www.greenend.org.uk/rjk/sftp/sftpversions.html>.
 .
 Features beyond the v3 set depend on suitable client support. A list of
 clients and the versions they support is at
 <http://www.greenend.org.uk/rjk/sftp/sftpimpls.html>.
 .
 NB! This server is currently experimental and still under development.
 Don't trust your critical data to it. The code has an extensive and
 growing test suite (invoke 'make check' to run it) but bugs may yet
 remain.