tools lib traceevent: Man page for tep_strerror()

tools lib traceevent: Man page for tep_strerror()

Create man page for tep_strerror() libtraceevent API.

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/20190503091119.23399-10-tstoyanov@vmware.com
Link: http://lkml.kernel.org/r/20190510200107.371692630@goodmis.org
[ Added "always" to state it doesn't matter if it is POSIX or GNU ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>