Added new man pages, describing function related libtraceevent APIs:

  tep_register_function(),
  tep_register_print_string(),
  tep_find_function(),
  tep_find_function_address(),
  tep_set_function_resolver(),
  tep_reset_function_resolver()
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/20190503091119.23399-12-tstoyanov@vmware.com
Link: http://lkml.kernel.org/r/20190510200107.701962205@goodmis.orgSigned-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>