Bring the following change from the illumos-joyent repository:

commit 78e24ab6803bbe11ba37642624e1498ede5b239d
Author: Bryan Cantrill <bryan@joyent.com>
Date:   Thu Oct 31 01:20:54 2013

    OS-1688 DTrace count() with histogram
    OS-2360 DTrace full width distribution histograms
    OS-2361 DTrace frequency trails

MFC after:	2 weeks