Implement -Wimplicit-fallthrough (version 9)

[Eric Botcazou]

> The intent has been that we catch the most common forms, but still require
> it not to be complete free form.  Because, as experience shows, people are
> extremely creative in these comments, and it is not very good idea to
> support everything.  For ... fall through ... , what is the purpose of
> those ...s?

No idea, but it has been there for a while and seems perfectly reasonable.
IMO any sentence containing "fall" and "through/thru/etc" on the same line 
should be accepted, otherwise it's just misplaced pickiness.

-- 
Eric Botcazou