Shared symbolizer between several processes

[dothebart]

The ArangoDB CI will launch local clusters, which conist of several instances of the same programm.
Running them with *san will cause them to launch a symbolizer sub-process each, which may eat up lots of resources.

@mpoeter implemented a simple server bridging the symboliser to a simple HTTP-API, and a simple client that will be launched alongside with the other processes instead.

https://github.com/arangodb/arangodb/tree/devel/utils#readme describes their usage.
Maybe a similar approach may be used via llvm directly?

If not - I leave this here for other people with similar issues.

Thanks for LLVM and the sanitizer toolchains, they make all our lives so much easier.