Allow control variable access in the fetchcallback even if papi is not running

Also fix a small issue in papi_store for papi.control.disable, we shouldn't
return PM_ERR_CONV if it's the first metric we compare against.

*src/pmdas/papi/papi.c
Return 'No Values Available' if metric is not active

*src/pmdas/papi/papi.c - in fetchcallback check to make sure the position is >=0
Fix adding papi metrics

*src/pmdas/papi/papi.c - currently when we add enlarge papi_info,
		       	 we increase the size with a realloc, and then
			 memset the contents to zero.  Normally this would
			 be fine, however the .position member variable
			 (which represents the position in the values[] array)
			 is valid when set to zero (normally a negative number
			 when not in use for that metric).  Check that the
			 papi_info element we're trying to add also has a
			 non-zero papi_event_code before adding.
Add checks that current events are available on hardware and not already in eventset

*src/pmdas/papi/papi.c - add checks to ensure papi events specified are available
		       	 on the hardware before we actually go to add them
			 add debug message for when they aren't actually available
			 also add a check that we haven't already added the event
			 before making an effort to do so
Return PM_ERR_CONV in the case of a metric being disabled that doesn't exist

*src/pmdas/papi/papi.c - return an error code for the case where
		       	 papi.control.disable "I_DONT_EXIST" is passed
Merge branch 'lberk/lberk-merge' of ../pcpfans into lberk-merge
PAPI PMDA updates and pmstore-based testing additions

New tests for pmda papi and ensure the value exported for
the control metrics (fetch) is not the tokenized variant.
Fix GUI tool builds for Mac OS X resources
Add not-yet-implemented to the libpcp_pmda fetch quiet errors
Make PCP_WHICH_PROG default to /usr/bin/which once more

Using "type" as the default is causing spurious diagnostics
failures on some platforms (f20 at least) as this sometimes
includes the shell path hashed/not state in the output.