LLVM 8.0 released

LLVM 8.0 has been released. This release contains the work on trunk up to Subversion revision r351319, plus work on the release branch. It's the result of the LLVM community's work over the past six months, including: speculative load hardening, concurrent compilation in the ORC JIT API, no longer experimental WebAssembly target, a Clang option to initialize automatic variables, improved pre-compiled header support in clang-cl, the /Zc:dllexportInlines- flag, RISC-V support in lld. And as usual, many bug fixes, optimization and diagnostics improvements, etc.