Merge llvm, clang, lld, lldb, compiler-rt and libc++ r305145, and update
build glue.

Update llvm to trunk r290819 and resolve conflicts.

Merge llvm trunk r238337 from ^/vendor/llvm/dist, resolve conflicts, and
preserve our customizations, where necessary.

Merge llvm 3.6.0rc1 from ^/vendor/llvm/dist, merge clang 3.6.0rc1 from
^/vendor/clang/dist, resolve conflicts, and cleanup patches.

Import LLVM/clang from vendor stripped of docs/ test/ website/ www/ examples/
in llvm/ and/or llvm/contrib/clang/ respectively.

Approved by: ed (mentor)
Approved by: core