perf script: Add general python handler to process non-tracepoint events

This patch just follows Robert Richter's idea and the commit 37a058ea


	"perf script: Add generic perl handler to process events"
to similarly add a python handler for general events other than tracepoints.

For non-tracepoint events, this patch will try to find a function named
"process_event" in the python script, and pass the event attribute,
perf_sample, raw_data in format of raw string. And the python script can
use "struct" module's unpack function to disasemble the needed info and process.

Signed-off-by: Feng Tang <feng.tang@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1344419875-21665-2-git-send-email-feng.tang@intel.com
[ committer note: Fixed up wrt da378962

, i.e. pevent parm in script event handlers ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>