Log Message:
Update chrony to version 1.31.1. For a full list of changes
since 1.29 see file NEWS in the distfile.

Security fixes since 1.29:

* Modify chronyc protocol to prevent amplification attacks (CVE-2014-0021)
  (incompatible with previous protocol version, chronyc supports both)
* Protect authenticated symmetric NTP associations against DoS attacks
  (CVE-2015-1799)
* Fix access configuration with subnet size indivisible by 4 (CVE-2015-1821)
* Fix initialization of reply slots for authenticated commands (CVE-2015-1822)