[7.0.0 Release] Release Candidate 1 source, docs, and binaries available

Hello everyone,

Source, docs, and binaries for LLVM-7.0.0-rc1 are now available at
http://prereleases.llvm.org/7.0.0/#rc1

I'll add more binaries as they become available.

Please try it out and report any problems as bugs marked as blockers
of https://llvm.org/PR38406

Thanks,
Hans