man5/perfevent: Added documentation for perfevent.conf
man5/perfevent: Added documentation for perfevent.conf

This patch adds documentation for alternate group events and scaling
support for the base events in derived events.

Signed-off-by: Hemant Kumar <7123f6a6628a9fc84f20db1d8af7bbec27c94c78@linux.vnet.ibm.com>

wuliming/pcp,adfernandes/pcp,adfernandes/pcp,wuliming/pcp,wuliming/pcp,adfernandes/pcp,wuliming/pcp,adfernandes/pcp,wuliming/pcp,adfernandes/pcp,wuliming/pcp,adfernandes/pcp,adfernandes/pcp,wuliming/pcp,adfernandes/pcp,wuliming/pcp