Introduce a *draft* of a code of conduct for the LLVM community and the

associated reporting guide.

I want to emphasize that at this point these are just drafts!

This is the result of very extended discussion on the mailing lists on
several different threads:
http://lists.llvm.org/pipermail/llvm-dev/2015-October/091218.html
http://lists.llvm.org/pipermail/llvm-dev/2016-May/099120.html
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20151019/307070.html

The reporting guide in particular I anticipate will be shaped somewhat
by the advisory committee when they are selected. But hopefully this
serves as a good starting point and good guidance while the advisory
committee is being sorted out.

I'd like to thank all the folks who contributed to this. Many, *many*
people worked to help with drafting, wording, suggestions, and edits.
Also, this is based on widely used existing codes of coduct as mentioned
in the text, and the original authors of those deserve many thanks as
well.

Differential Revision: http://reviews.llvm.org/D13741

llvm-svn: 274268