pcp updates - pcp-iostat -u (non-interpolating replay) + QA

[Mark Goodwin <mgoodwin@xxxxxxxxxx>]

This adds -u flag to pmiostat to replay archives at native sampling interval
(i.e. in non-interpolating mode). Plus QA to exercise it and man page update.

Changes committed to git://git.pcp.io/mgoodwin/pcp master


commit c1a856f01a9433f1a037be4ab2c3f1fe6d79248d
Author: Mark Goodwin <mgoodwin@xxxxxxxxxx>
Date:   Wed Feb 10 15:54:57 2016 +1100

    qa: pmiostat additional testing in qa/1099 for new -u flag
    
    Testing pmiostat in non-interpolation mode
commit d8fdf340a692d53ec530372c1df17981825351da
Author: Mark Goodwin <mgoodwin@xxxxxxxxxx>
Date:   Wed Feb 10 13:00:39 2016 +1100

    pmiostat: support uninterpolated archive replay with -u flag
    
    The -u flag disables interpolation when replaying an archive.
    Instead the native underlying replay interval in the archive
    is used. See the -u option in the man page for details.