* New upstream stable release (52.0build2)
  - see USN-3216-1
* Update debian/patches/revert-upstream-search-engine-changes.patch
* Unconditionally build-dep on libffi-dev
* Drop */browser/components from firefox.install.in, browsercomps was merged
  into xul - https://hg.mozilla.org/mozilla-central/rev/4006b190b344
* Refresh patches
  - update debian/patches/unity-menubar.patch
  - update debian/patches/revert-upstream-search-engine-changes.patch
  - update debian/patches/ubuntu-bookmarks.patch