Merge from head:

Merge from head:
r227785:
  - Reduce severity for all ARP events, that can be triggered from remote
    machine to LOG_NOTICE. Exception left to "using my IP address".
  - Fix multicast ARP warning: add newline and also log the bad MAC address.

  Tested by:    Alexander Wittig <wittigal msu.edu>

r227790:
  Be more informative for "unknown hardware address format" message.

  Submitted by: Andrzej Tobola <ato iem.pw.edu.pl>

git-svn-id: svn://svn.freebsd.org/base/stable/9@233265 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f