perf trace: Add mmap2 handler

5c5e854b changed perf_event__synthesize_mmap_events to generate MMAP2
events. Since perf-trace does not have a handler for it it dies with a
segfault when trying to process files:

perf trace -i /tmp/perf.data
Segmentation fault

Signed-off-by: David Ahern <dsahern@gmail.com>
Link: http://lkml.kernel.org/r/1379900700-5186-4-git-send-email-dsahern@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>