• ntohs() returns unsigned value.
• use strlcpy.
• snprintf can return negative value, so cope with it.
• tweak interface index on interface locals (ff01::/16).
• removed unused macros.
• removed a macro that uses only once (in a trivial context).
• explicitly say goodbye to ENI_xxx.
• constify struct afd.

Obtained from: KAME
MFC after: 1 week