Update INSTALL.txt with information on using PAPI with Perf Events.
Update INSTALL.txt with information on using PAPI with Perf Events.

pyrovski/papi,arm-hpc/papi,arm-hpc/papi,arm-hpc/papi,pyrovski/papi,arm-hpc/papi,pyrovski/papi,pyrovski/papi,arm-hpc/papi,arm-hpc/papi,pyrovski/papi,pyrovski/papi,arm-hpc/papi,pyrovski/papi,pyrovski/papi