Re: Sort support for macaddr8

so, if what you say is true and it is either not worth it or
potentially a breaking change to make macaddr8 pass-by-value and
adding abbreviated sort support has the potential to avoid "pointer
chasing" and guarantee equivalent relative performance for macaddr8
and macaddr, then that seems worth it.

With regard to macaddr8_abbrev_convert() and memset(), I attached a patch
with the memset() removed, since it is superfluous here.

macaddr8_cmp_internal() already existed before this patch and I noticed
that it explicitly returns int32 whereas the return type of
macaddr_cmp_internal() is just specified as an int. I was wondering why.

I also noticed that the prototype for macaddr8_cmp_internal() was not
at the top of the file with the other static function prototypes. I
added it there, but I wasn't sure if there was some reason that it was
like that to begin with.