kernel autodetect: rework RTAI detection
kernel autodetect: rework RTAI detection

/dev/rtai_shm isnt used anymore, and it would have required the RTAI
modules to be insert to reliably detect RTAI.

Instead, use differences in the /proc/ipipe directory to tell RTAI from
Xenomai:  Xenomai has /proc/ipipe/Xenomai and /dev/rtheap both of which
RTAI doesnt have; so use this difference for now

This is going to remain heuristic.

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