Add an option to perf record to record running/enabled time for read
events, similar to what stat does.

This is useful to understand multiplexing problems.

Right now the report support is not great, but at least report -D
already supports it.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1424819620-16043-1-git-send-email-andi@firstfloor.org
[ Fixed the Documentation entry to match the OPT_BOOLEAN one ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>