[LinuxPPS] ntp-4.2.6 and linuxpps

[Remco dB]

OK, thanks Hal and Reg for the feedback. 

Today I upgraded to ntpd 4.2.6 on a 2.6.27.5 system with LinuxPPS. 

This worked flawlessly, and indeed, the 'recovery time' is somewhat 
longer, i.e. the offset runs more smooth towards (almost) zero. 
It seems that the loopfilter may be modified to prevent an overshoot?

By the way, my desktop machine, which is locked against a DCF77
receiver, now jitters between +/- 1 msec with 4.2.6. This was +/- 5 msec.