clang-tutor: out-of-tree examples for teaching & learning

Hello all,

New Clang tutorial - please share! :slight_smile:

Over the last few months I have been working on *clang-tutor*. It is a collection of out-of-tree plugins for Clang (and LibTooling based tools). You can find it here:

https://github.com/banach-space/clang-tutor

I am hoping that *clang-tutor* will make Clang a bit easier for people to get started with. Also, I intend to keep it up to date so that it stays relevant.

Quick summary:
* complete - includes CMake build scripts, LIT tests and CI set-up
* out of tree - builds against a binary Clang installation (no need to build Clang from sources)
* modern - based on LLVM 10 (and updated with every release)

There's plenty of comments in the source files and README.md - hopefully these will make it easy to follow.

Happy hacking!

-Andrzej