[Bug c/77909] New: -Wimplicit-fallthrough: accept more comment variants

[marc.mutz at kdab dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77909

            Bug ID: 77909
           Summary: -Wimplicit-fallthrough: accept more comment variants
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: marc.mutz at kdab dot com
  Target Milestone: ---

In QtBase, we have several unrecognised forms of fall-through comments, which
are quite common, and probably should be recognized, too:

- interpunctation: "fall through" followed by [;:!]

- prefix with "else", "otherwise", or "intentionl(ly)"

- "no break" instead of "fall through"