tools lib traceevent: Add support for extracting trace_clock in report

If trace-cmd extracts trace_clock, trace-cmd reads trace_clock data from
the trace.dat and switches outputting format of timestamp for each
trace_clock.

Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20130424231305.14877.86147.stgit@yunodevel


Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>