Add checks that current events are available on hardware and not already in eventset
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

aeg-aeg/pcpfans,mbaldessari/pcp,aeg-aeg/pcpfans,tjanez/pcp,mbaldessari/pcp,edwardt/pcp,wuliming/pcp,tjanez/pcp,edwardt/pcp,prasincs/pcp,edwardt/pcp,andyvand/cygpcpfans,aeg-aeg/pcpfans,prasincs/pcp,mbaldessari/pcp,edwardt/pcp,edwardt/pcp,adfernandes/pcp,mbaldessari/pcp,andyvand/cygpcpfans,prasincs/pcp,andyvand/cygpcpfans,tjanez/pcp,aeg-aeg/pcpfans,prasincs/pcp,wuliming/pcp,aeg-aeg/pcpfans,edwardt/pcp,adfernandes/pcp,mbaldessari/pcp,aeg-aeg/pcpfans,adfernandes/pcp,edwardt/pcp,prasincs/pcp,tjanez/pcp,prasincs/pcp,adfernandes/pcp,prasincs/pcp,andyvand/cygpcpfans,edwardt/pcp,mbaldessari/pcp,wuliming/pcp,adfernandes/pcp,andyvand/cygpcpfans,andyvand/cygpcpfans,aeg-aeg/pcpfans,wuliming/pcp,aeg-aeg/pcpfans,tjanez/pcp,adfernandes/pcp,andyvand/cygpcpfans,wuliming/pcp,wuliming/pcp,wuliming/pcp,prasincs/pcp,tjanez/pcp,tjanez/pcp,wuliming/pcp,adfernandes/pcp,andyvand/cygpcpfans,adfernandes/pcp,tjanez/pcp