Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFV: libpcap 1.3.0.

MFC after: 4 weeks

Merge from vendor branch: update libpcap to 1.2.1.

MFC after: 2 weeks

Merge libpcap 1.0.0.

This commit was generated by cvs2svn to compensate for changes in r172677,
which included commits to RCS files with non-trunk default branches.