Changes from 5.8:
- Algorithm:
  - Multi-Level Dijkstra:
    - Plugins supported: `table`
    - Adds alternative routes support (see [#4047](https://github.com/Project-OSRM/osrm-backend/pull/4047) and [3905](https://github.com/Project-OSRM/osrm-backend/issues/3905)): provides reasonably looking alternative routes (many, if possible) with reasonable query times.
- API:
  - Exposes `alternatives=Number` parameter overload in addition to the boolean flag.
  - Support for exits numbers and names. New member `exits` in `RouteStep`, based on `junction:ref` on ways
  - `Intersection` now has new parameter `classes` that can be set in the profile on each way.
- Profiles:
  - `result.exits` allows you to set a way's exit numbers and names, see [`junction:ref`](http://wiki.openstreetmap.org/wiki/Proposed_features/junction_details)
  - `ExtractionWay` now as new property `forward_classes` and `backward_classes` that can set in the `way_function`.
     The maximum number of classes is 8.
- Node.js Bindings:
  - Exposes `alternatives=Number` parameter overload in addition to the boolean flag
  - Expose `EngineConfig` options in the node bindings
- Tools:
  - Exposes engine limit on number of alternatives to generate `--max-alternatives` in `osrm-routed` (3 by default)
- Infrastructure
  - STXXL is not required to build OSRM and is an optional dependency for back-compatibility (ENABLE_STXXL=On)
  - OpenMP is only required when the optional STXXL dependency is used
- Bug fixes:
  - #4278: Remove superflous continious instruction on a motorway.