tools lib traceevent: Man pages for APIs used to extract common fields from a record

Create man pages for libtraceevent APIs:

 tep_data_type(),
 tep_data_pid(),
 tep_data_preempt_count(),
 tep_data_flags()

Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: linux-trace-devel@vger.kernel.org
Link: http://lore.kernel.org/linux-trace-devel/20190503091119.23399-26-tstoyanov@vmware.com
Link: http://lkml.kernel.org/r/20190510200110.284281830@goodmis.org


[ Fixed missing T in description of NOSUPPORT flag ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>