Define local licenses

Gerrit core fixed license generation in
c535dd6e231821a940ef692ca36d8182b30ff80c, which made the build of
x-docs fail [1], as the local licenses have not been defined. We now
define them to allow building against current gerrit core master.

[1] Error message was (wrapped long lines)

  BUILD FAILED: Couldn't get dependency '//lib:LICENSE-mbassador' of
  target '//plugins/x-docs/lib/docx4j:mbassador': The build file that
  should contain //lib:LICENSE-mbassador has already been parsed
  (/home/gerrit_builder/builds/master/gerrit/lib/BUCK), but
  //lib:LICENSE-mbassador was not found. Please make sure that
  //lib:LICENSE-mbassador is defined in
  /home/gerrit_builder/builds/master/gerrit/lib/BUCK.

See
  http://builds.quelltextlich.at/gerrit/nightly/master/2015-06-26/index.html#x-docs.jar
  http://builds.quelltextlich.at/gerrit/nightly/master/2015-06-26/x-docs.jar.build.stderr.txt

Change-Id: I96d666f6ce4bb8b1376bd7d89a9a6e837820dd3d