[mesa/f18] (3 commits) ...Merge branch 'f19' into f18

[Adam Jackson]

Summary of changes:

  5b216c7... Fix build with private LLVM (*)
  ac0fbf9... Enable llvmpipe even on non-SSE2 machines (#909473) (*)
  9db6e3c... Merge branch 'f19' into f18

(*) This commit already existed in another branch; no separate mail sent