Add RFC 8335 Definitions from Linux 5.13

RFC 8335 defines the network utility PROBE, which builds off of the
capabilities of Ping to query more detailed interface information from
networking nodes.

The definitions included in this patchset have been accepted into the
linux net-next branch and will be included in Linux 5.13. This
patchset adds the same definitions to the glibc for use in the
iputils package.

The relevant commits for the Linux definitions can be found here:
https://github.com/torvalds/linux/commit/e542d29ca81d005651680a0a697b72ca13ddc4cc
https://github.com/torvalds/linux/commit/750f4fc2a12f6632b5aa04526bf57fa06bfe8467



These changes have been tested by running the glibc tests on x86_64

Signed-off-by: Andreas Roeseler <andreas.a.roeseler@gmail.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>