Log Message:
security/ruby-sshkit: update to 1.21.0

Update ruby-sshkit: update to 1.21.0.
pkgsrc change: add "USE_LANGUAGES=	# none".

1.20.0 (2019-08-03)

* #468: Make upload! take a :verbosity option like exec does - @grosser

1.19.1 (2019-07-02)

* #465: Fix a regression in 1.19.0 that prevented ~ from being used in
  Capistrano paths, e.g. :deploy_to, etc. - @grosser

1.19.0 (2019-07-01)

* #455: Ensure UUID of commands are stable in logging - @lazyatom
* #453: as and within now properly escape their user/group/path arguments,
  and the command nested within an as block is now properly escaped before
  passing to sh -c. In the unlikely case that you were manually escaping
  commands passed to SSHKit as a workaround, you will no longer need to do
  this. See #458 for examples of what has been fixed. - @grosser
* #460: Handle IPv6 addresses without port - @will-in-wi

1.18.2 (2019-02-03)

* #448: Fix misbehaving connection eviction loop when disabling connection
  pooling - Sebastian Cohnen

1.18.1 (2019-01-26)

* #447: Fix broken thread safety by widening critical section - Takumasa Ochi