Update the PAPI_enum_event() Doxygen comments to reflect modern   values for the "modifier" parameter.
Update the PAPI_enum_event() Doxygen comments to reflect modern
  values for the "modifier" parameter.

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