Import Debian changes 2.1.0+dfsg-2.1

lua-cjson (2.1.0+dfsg-2.1) unstable; urgency=medium
.
  * Non-maintainer upload.
  * debian/control: Drop explicit Pre-Depends on multiarch-support
    (Closes: #870548).
.
lua-cjson (2.1.0+dfsg-2) unstable; urgency=low
.
  * Add debian/watch file.
.
lua-cjson (2.1.0+dfsg-1) unstable; urgency=low
.
  * Initial release. (Closes: #685591)