Still seeing "calcru: runtime went backwards" messages

[Poul-Henning Kamp]

I've updated the calibration code to be much more precise, let me know
if this helps or not.

Disregard all steps less than 2 microseconds for now.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.