rtapi_app: test if user is member of group xenomai
rtapi_app: test if user is member of group xenomai

xenomai-user threads only. This should give a hint what to do on
'Xenomai: binding failed: Operation not permitted.' errors

strahlex/machinekit,araisrobo/machinekit,cdsteinkuehler/MachineKit,cdsteinkuehler/linuxcnc,Cid427/machinekit,ArcEye/machinekit-testing,cdsteinkuehler/MachineKit,bobvanderlinden/machinekit,EqAfrica/machinekit,mhaberler/machinekit,araisrobo/machinekit,RunningLight/machinekit,cdsteinkuehler/MachineKit,mhaberler/machinekit,ArcEye/MK-Qt5,cdsteinkuehler/linuxcnc,ArcEye/machinekit-testing,RunningLight/machinekit,kinsamanka/machinekit,RunningLight/machinekit,cdsteinkuehler/MachineKit,EqAfrica/machinekit,ArcEye/MK-Qt5,Cid427/machinekit,unseenlaser/machinekit,EqAfrica/machinekit,RunningLight/machinekit,RunningLight/machinekit,EqAfrica/machinekit,RunningLight/machinekit,cdsteinkuehler/MachineKit,strahlex/machinekit,RunningLight/machinekit,strahlex/machinekit,bobvanderlinden/machinekit,araisrobo/machinekit,ArcEye/MK-Qt5,Cid427/machinekit,strahlex/machinekit,Cid427/machinekit,mhaberler/machinekit,araisrobo/machinekit,cdsteinkuehler/linuxcnc,bobvanderlinden/machinekit,Cid427/machinekit,kinsamanka/machinekit,cdsteinkuehler/linuxcnc,bobvanderlinden/machinekit,ArcEye/MK-Qt5,cdsteinkuehler/linuxcnc,ArcEye/MK-Qt5,mhaberler/machinekit,ArcEye/MK-Qt5,araisrobo/machinekit,ArcEye/MK-Qt5,kinsamanka/machinekit,unseenlaser/machinekit,araisrobo/machinekit,Cid427/machinekit,RunningLight/machinekit,ArcEye/machinekit-testing,mhaberler/machinekit,ArcEye/MK-Qt5,cdsteinkuehler/MachineKit,Cid427/machinekit,araisrobo/machinekit,EqAfrica/machinekit,unseenlaser/machinekit,kinsamanka/machinekit,ArcEye/machinekit-testing,mhaberler/machinekit,strahlex/machinekit,EqAfrica/machinekit,kinsamanka/machinekit,araisrobo/machinekit,bobvanderlinden/machinekit,unseenlaser/machinekit,kinsamanka/machinekit,unseenlaser/machinekit,araisrobo/machinekit,ArcEye/machinekit-testing,mhaberler/machinekit,ArcEye/machinekit-testing,bobvanderlinden/machinekit,kinsamanka/machinekit,cdsteinkuehler/linuxcnc,bobvanderlinden/machinekit,Cid427/machinekit,mhaberler/machinekit,EqAfrica/machinekit,ArcEye/machinekit-testing,ArcEye/machinekit-testing,bobvanderlinden/machinekit,unseenlaser/machinekit,strahlex/machinekit,unseenlaser/machinekit,strahlex/machinekit,EqAfrica/machinekit,kinsamanka/machinekit,unseenlaser/machinekit