Center Leap Smearing Interval

In NTPsec, the leap smearing occurs over the configured leapsmearinterval before the leap second:

See ntpd/ntp_timer.c:401: leap_smear.intv_start = leap_smear.intv_end - leap_smear.interval;

Google has proposed a standardized leap smear of 24 hours (i.e. leapsmearinterval 86400) centered on the leap second: https://developers.google.com/time/smear

I filed a similar bug report with NTP Classic: http://bugs.ntp.org/show_bug.cgi?id=3481