fix libevent on visual studio
fix libevent on visual studio

Change-Id: Iaf40206710173cea72ac6cb7a3636d91a4454096
Reviewed-on: http://gerrit.aldebaran.lan:8080/76
Reviewed-by: Dimitri Merejkowsky <1e4b13000fa8777df4cefd2fd8215187e3deb062@aldebaran-robotics.com>
Tested-by: Dimitri Merejkowsky <1e4b13000fa8777df4cefd2fd8215187e3deb062@aldebaran-robotics.com>

aldebaran/qibuild,dmerejkowsky/qibuild,dmerejkowsky/qibuild,dmerejkowsky/qibuild,aldebaran/qibuild,dmerejkowsky/qibuild,aldebaran/qibuild,dmerejkowsky/qibuild,aldebaran/qibuild