[Bug lto/65378] Tweak to wording of -Wodr message

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65378

--- Comment #1 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
(In reply to David Malcolm from comment #0)
[...]
> Message in question is here in ipa-devirt.c:
>   if (!warning_at (DECL_SOURCE_LOCATION (TYPE_NAME (t1)), OPT_Wodr,
> 		   "type %qT violates one definition rule",
> 		   t1))
and in 5 other places in that file.