pcp updates: add -R flag to pmiostat for reg-ex search

[Nikhil Kshirsagar <nkshirsa@xxxxxxxxxx>]

Implements the -R option for pmiostat, along with man page and usage
updates.

Changes committed to https://github.com/nkshirsagar/pcp_patch

commit 6c492cc3eb26bf8e131391a36b30317650f57b0d
Author: Nikhil Kshirsagar <nkshirsa@xxxxxxxxxx>
Date:   Mon Apr 25 13:20:15 2016 +0530

    Adding -R option to pmiostat.
   
    The -R option will allow users to provide a regular expression
    pattern to match the device names. Only devices matching the
    pattern will be displayed.


Regards,
Nikhil.