LLVM 6.0.0 released

Version 6.0.0 of the LLVM compiler suite is out."This release is the result of the community's work over the past sixmonths, including: retpoline Spectre variant 2 mitigation,significantly improved CodeView debug info for Windows, GlobalISel bydefault for AArch64 at -O0, improved scheduling on several x86micro-architectures, Clang defaults to -std=gnu++14 instead of-std=gnu++98, support for some upcoming C++2a features, improvedoptimizations, new compiler warnings, many bug fixes, and more."