perf probe: Add --list option for listing current probe events

Add --list option for listing currently defined probe events
in the kernel. This shows events in below format;

 [group:event]	<perf-probe probe-definition>

for example:

 [probe:schedule_0]	schedule+30 cpu

Note that source file/line information is not supported yet.
So even if you added a probe by line, it will be shown in
<symbol+offset>.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Frank Ch. Eigler <fche@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jason Baron <jbaron@redhat.com>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20091201002017.10235.76575.stgit@harusame>
Signed-off-by: Ingo Molnar <mingo@elte.hu>