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

Hello all,

New LLVM tutorial - please share! :slight_smile:

Over the last few months I have been working on *llvm-tutor*. It is a
collection of out-of-tree passes/plugins and tools for LLVM. You can
find it here:

I am hoping that *llvm-tutor* will make LLVM more accessible. It should
be particularly relevant to everyone keen on leveraging LLVM for their
own out-of-tree projects.

Quick summary:
* complete - includes CMake build scripts, LIT tests and CI set-up
* out of tree - builds against a binary LLVM installation (no need to
build LLVM from sources)
* modern - based on LLVM 9 (and updated with every release)

There's plenty of comments in the source files and the README.md file.
Also, during the recent LLVM Dev Meeting I presented a tutorial based on
llvm-tutor ("Writing an LLVM Pass: 101"). I'll post a link to the video
and slides once those are available.

Happy hacking!

-Andrzej