[PATCH] Fix ether_ntoa() output format

[Roland McGrath]

This change may need further justification.  It is the de facto norm that
MAC address notation is accepted with one-digit fields, so there is no
particular reason to think that the existing behavior causes any problems.
Conservatism/paranoia says don't perturb in fear of unintended effects on
existing users.  The middle road would be to change with a new symbol
version and keep the existing behavior for existing binaries.

OTOH, recent FreeBSD uses %02x format so it's likely that the change won't
cause trouble.  So I don't really have an objection.

The log entry is inadequate.  Pretty much any entry that says "fix foobar"
is wrong.  It should describe the change, which is very simple to describe
in this case ("Use %02x rather than %x for each address byte.").

This user-visible change needs a BZ report (which should give
justification, preferably something practical rather than just a vague
reference to a non-binding not-really-a-spec) and BZ# tag in its log entry.