Merge branch 'stable-2.11' into stable-2.12

* stable-2.11:
  Use bucklets-provided constant to refer to Plugin API

Change-Id: I4e7154bd492a0f2447d3bb41d5aad5731066ca64
tree: 316a3966b6ff406ea0d48eae9801a422b8fcd187
  1. lib/
  2. src/
  3. .buckconfig
  4. .gitignore
  5. BUCK
  6. LICENSE