Import Debian changes 0.9.0-1

gxkb (0.9.0-1) unstable; urgency=medium
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  * New upstream release.
    + Switch to GTK3. (Closes: #967515)
  * Bump Standards-Version to 4.5.1 (no changes needed)
  * d/control: Add Rules-Requires-Root.
  * Bump version d/watch.