[4.0.0 Release] Release Candidate 3 source and binaries available

Source, binaries and docs for LLVM-4.0.0-rc3 are now available at
http://www.llvm.org/pre-releases/4.0.0/#rc3

Please file any issues as blockers of http://llvm.org/pr31622.

Hopefully we can get to the final release soon.

Cheers,
Hans