Bugfix and small feature release.

First release in some time. Fixing lots of bugs and adds a few new
features. Below are the highlights.

Features:
* [GH-301] support rename extension for server
* [GH-332] Added a ClientOption to determine whether to use Fstat or Stat
* [GH-315] make SFTP extensions configurable

Bugfixes:
* [GH-291] Wrong S_IFMT mask when converting filemode bits to os.FileMode
* [GH-295] sftp resume produces corrupted files
* [GH-298] Extensions are not announced by the server
* [GH-329] fix S_IFMT value on windows, plan9 and js/wasm
* [GH-325] Request.Attributes() panics when called with the Attr slice empty
* [GH-309] fix: received packet too long

Thanks to all the contributors. Your time and patience is appreciated.

go modules update

make client more resilient with servers that don't support full protocol

client can now detect sftp connection close

Implments a clintConn.Wait() method.
Fixes: #278

Thanks @wutzx for the PR.

fixes tests to run on windows

refactor opening files/dirs in request-server

Minor version bump due to a pretty heavy refactoring of the
request-server's handing of open packets. It now calls through to the
handler to initialize the reader/writer/lister objects when it receives
the open packet. This should be transparent and was done in relation to
a bug fix, but it is a pretty major refactor so the minor version bump.

Fixed #280; Request.WithContext() deadlock when called from handler

Fix race issue in request server.

Fixes issue with lock/race condition in request server get/put.

bugfix release

fixes #264; issue with rename in request example
fixes #265; open/stat packet race condition (fixes sshfs as client)

Bugfix release.

Fixes #260; packet ordering bug with ws-ftp client
Adds gcc-go AIX support.

New go module conformant version tag.

Fixes #261

Bugfixes, docs and concurrent request option

- Fixes
     This created an unwanted C-go dependency.
     Plan to replace it with an callback/option.
Make sure to cancel context on requests with reader/writers that support
io.Closer.

- New features
Started improving documentation of Request based server.

new MkdirAll; fixes for fsetstat, attributes, list

Client.MkdirAll method mirroring os.MkdirAll
Fix #243, flags and attributes not being set for fsetstat calls in
    request server
Fix #245, request server attributes methods now use exported types
Fix #240, fix issue with request server file list returning early

minor new feature (username/groupname lookup)

On Unix systems the server code will now attempt to lookup the username
and group name for the file longname value (used for ls -l output).

small bugfix release

Fixes issue with unsupported extended packets causing the server to
abort the session instead of returning an unsupported error packet.

Fix ordering issue with Request.close calls that canceled the context
before trying to close the reader and writer.

bugfix and small feature release

Fixes #234: fix client deadlock on server death during writes

Feature: Added ability to set MaxPacket size for the clients to values
outside those accepted by Openssh's SFTP server. To support servers with
differing capacities.

New context.Context in Request server

Added context.Context support for the Request server.
Remove unnecessary gcc special cases.

New errors, documentation and dropping go<=1.7

New request-server errors for explicitly controlling returned status code.
Drop go <= 1.7 support.
Documentation improvements.

Small feature and bugfix release.

Feature: Add helper functions to the request object for working with
bitmask flags and file attributes.

Fix: Corrctly handled errors coming from the backend on file Open w/
create flag.

New bugfix release. Mainly bug w/ windows volumes.

Fixes issue #217; Fix volume name mangling on windows

Open-packet's pflags (file opening flags) now saved in Request.Flags
since in cases of SSH_FXF_CREAT being set a 0 len Write call is made.

Also continuing some refactoring to simplify and clean up the request
based code. In this case I removed an unnecessary data structure storing
packet data.

New bugfix release. Fixes request-server issues.

Fix issue #214; request-server doesn't handle uploads of empty files
Fix issue #215; request-server: problem with Request.setFileState()

Also a small refactor of the Request struct and how it is stored and
updated. Simplifies things and reduces garbage.

New bugfix and minor feature release

Fixes #207, a problem with the server returning bad paths
Adds PR #213, adds PosixRename (OpenSsh extention) to client