tools lib traceevent: Man pages for registering print function

tools lib traceevent: Man pages for registering print function

Create man pages for libtraceevent APIs:

  tep_register_print_function()
  tep_unregister_print_function()

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://lkml.kernel.org/r/20190510200107.857252818@goodmis.org
Link: http://lore.kernel.org/linux-trace-devel/20190503091119.23399-13-tstoyanov@vmware.com
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>