Patch to support extended characters in C/C++ identifiers

[Joseph Myers]

On Thu, 12 Sep 2019, Lewis Hyatt wrote:

> Attached is a single patch relative to current trunk that incorporates all of
> your feedback. I gzipped it like last time just in case the invalid UTF-8 in
> the tests presents a problem. The code changes are the same as before other
> than comments.
> 
> The documentation is now updated... there were a couple other places that also
> seemed reasonable to me to update, hope it sounds OK.

Thanks, I've now committed this patch.

-- 
Joseph S. Myers
joseph@codesourcery.com