Upgrades LLVM 3.8.1 -> LLVM 3.9.1
Upgrades LLVM 3.8.1 -> LLVM 3.9.1

LLVM 3.9.1 is now packaged in mason: https://github.com/mapbox/mason/issues/308
Upgrade our Clang compiler to the latest stable release.

In osrm: https://github.com/Project-OSRM/osrm-backend/pull/3526

oxidase/node-osrm,oxidase/node-osrm,oxidase/node-osrm,Project-OSRM/node-osrm,Project-OSRM/node-osrm,Project-OSRM/node-osrm