Add comment to PAPI_num_counters() documentation about use of PAPI_num_cmp_hwctrs() for component counters.
Add comment to PAPI_num_counters() documentation about use of PAPI_num_cmp_hwctrs() for component counters.

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