[Bug c++/85707] -Wclass-memaccess should excempt safe usage inside of a class and its friends

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85707

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The Position type is trivially-copyable, so IMHO shouldn't warn about uses of
memset/memcpy, but I'm not sure what the conditions for the warning are.