MFC r298695: MFV r298691: ntp 4.2.8p7.

Security: CVE-2016-1547, CVE-2016-1548, CVE-2016-1549, CVE-2016-1550
Security: CVE-2016-1551, CVE-2016-2516, CVE-2016-2517, CVE-2016-2518
Security: CVE-2016-2519
Security: FreeBSD-SA-16:16.ntp
With hat: so