[Bug lto/48200] Implement function attribute for symbol versioning (.symver)

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=48200

--- Comment #33 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
See https://mails.dpdk.org/archives/dev/2019-September/144749.html also.