Add support for decoding Intel Processor Trace packets.

This essentially provides intel_pt_get_packet() which takes a buffer of
binary data and returns the decoded packet.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1437150840-31811-3-git-send-email-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>