perf: add prefix to event name

  add prefix p_ or r_ to event name to distinguish the probe and retprobe
events. So it will look like:

  # ./perf probe -x /lib64/libc.so.6 malloc
  probe_libc:p_malloc  (on 0x7f2b0)
  # ./perf probe -x /lib64/libc.so.6 malloc%return
  probe_libc:r_malloc  (on 0x7f2b0%return)

  # cat uprobe_events
  p:probe_libc/p_malloc /lib64/libc.so.6:0x000000000007f2b0
  r:probe_libc/r_malloc /lib64/libc.so.6:0x000000000007f2b0

Signed-off-by: Anton Arapov <anton@redhat.com>
uretprobes: implement uretprobe for trace_event interface

	ssia.

Signed-off-by: Anton Arapov <anton@redhat.com>
dump

Signed-off-by: Anton Arapov <anton@redhat.com>