doxygen: exclude useless symbols

Change-Id: Ic69c05ac69aa35f36cc8ed872331e5fc75ba6181
Reviewed-on: http://gerrit.aldebaran.lan/50569
Reviewed-by: pdaouadi <pdaouadi@aldebaran-robotics.com>
Tested-by: pdaouadi <pdaouadi@aldebaran-robotics.com>
Reviewed-on: http://gerrit.aldebaran.lan/50579