Mimic unix dlclose behavior on windows.

Change-Id: Ib20433d9150c40709dacd9437e8fd01b86317d6f
Reviewed-on: http://gerrit.aldebaran.lan:8080/18081
Reviewed-by: cgestes <gestes@aldebaran-robotics.com>
Tested-by: proullon <proullon@aldebaran-robotics.com>