pcp update: papi-pmda dynamic metrictab[]

["Frank Ch. Eigler" <fche@xxxxxxxxxx>]

Hi -

Thanks to kenj's fine work from last week, this patch from pcpfans.git
simplifies the papi pmda to eliminate the malloc'd metrictab[].

I didn't publish this patch earlier because during regression
testing, the linux-proc pmda crashes.  But a brief investigation
showed that this particular failure (a memory corruption during the
fetch / value-stuff loop) also exists in git/dev pcp as per lberk's
fine rawhide-pcp build, so this change was not responsible.


commit ede409944fe58fef2eaba2dd275a0899745bb9bd
Author: Frank Ch. Eigler <fche@xxxxxxxxxx>
Date:   Sun Nov 23 19:50:26 2014 -0500

    papi pmda: use dynamic metric description
    
    Using kenj's commit #f856e2c171, it becomes possible to avoid
    allocating a metrictab[] in the pmda, when it is so easy to generate
    each pmDesc on demand.  This is done by having the pmdaFetch()
    function in libpcp_pmda fall back to the pmdaInterface->desc callback
    (if set), if a metrictab[] was not specified during pmdaInit().
    
    The papi pmda is converted to this scheme.  (Also, multiplexing is
    turned back on by default, as per the qa/967 test case, and .gitignore
    is extended with help.* stuff.)