latencyplot: add plot option based on hal timedelta component
latencyplot: add plot option based on hal timedelta component

The rtai/testsuite/user/latency/run connection returns EOF for
unknown reasons when the process is backgrounded.

So mark it declining (with respect to this script) and use
hal timedelta as default.

Using hal timedelta makes some options possible too:

Usage:
      latencyplot --help | -?      (this)
      latencyplot --rtai           (declining usage, uses rtai testsuite)
      latencyplot --hal [Options]  (default, uses hal timedelta)

Options:
      --time mS  (report interval, default: 1000)
      --relative (relative clock time (default))
      --actual   (actual clock time)

narogon/linuxcnc,cnc-club/linuxcnc,narogon/linuxcnc,jaguarcat79/ILC-with-LinuxCNC,araisrobo/linuxcnc,bmwiedemann/linuxcnc-mirror,mhaberler/machinekit,ArcEye/machinekit-testing,RunningLight/machinekit,ArcEye/machinekit-testing,unseenlaser/linuxcnc,cdsteinkuehler/linuxcnc,cdsteinkuehler/linuxcnc,bobvanderlinden/machinekit,ArcEye/machinekit-testing,Cid427/machinekit,ianmcmahon/linuxcnc-mirror,bobvanderlinden/machinekit,jaguarcat79/ILC-with-LinuxCNC,ArcEye/MK-Qt5,bobvanderlinden/machinekit,EqAfrica/machinekit,kinsamanka/machinekit,unseenlaser/machinekit,ArcEye/MK-Qt5,ikcalB/linuxcnc-mirror,narogon/linuxcnc,mhaberler/machinekit,Cid427/machinekit,ArcEye/machinekit-testing,ikcalB/linuxcnc-mirror,strahlex/machinekit,cnc-club/linuxcnc,Cid427/machinekit,unseenlaser/machinekit,unseenlaser/machinekit,Cid427/machinekit,ianmcmahon/linuxcnc-mirror,cdsteinkuehler/linuxcnc,bobvanderlinden/machinekit,ArcEye/MK-Qt5,kinsamanka/machinekit,RunningLight/machinekit,ArcEye/machinekit-testing,cdsteinkuehler/MachineKit,bobvanderlinden/machinekit,unseenlaser/linuxcnc,EqAfrica/machinekit,ArcEye/MK-Qt5,ArcEye/MK-Qt5,mhaberler/machinekit,cnc-club/linuxcnc,aschiffler/linuxcnc,kinsamanka/machinekit,ianmcmahon/linuxcnc-mirror,EqAfrica/machinekit,ianmcmahon/linuxcnc-mirror,EqAfrica/machinekit,jaguarcat79/ILC-with-LinuxCNC,ikcalB/linuxcnc-mirror,araisrobo/machinekit,unseenlaser/machinekit,mhaberler/machinekit,cnc-club/linuxcnc,araisrobo/machinekit,EqAfrica/machinekit,araisrobo/machinekit,jaguarcat79/ILC-with-LinuxCNC,cdsteinkuehler/MachineKit,unseenlaser/machinekit,mhaberler/machinekit,RunningLight/machinekit,unseenlaser/linuxcnc,ArcEye/MK-Qt5,bmwiedemann/linuxcnc-mirror,cdsteinkuehler/MachineKit,ianmcmahon/linuxcnc-mirror,Cid427/machinekit,EqAfrica/machinekit,ikcalB/linuxcnc-mirror,strahlex/machinekit,ArcEye/machinekit-testing,araisrobo/machinekit,RunningLight/machinekit,kinsamanka/machinekit,cdsteinkuehler/MachineKit,araisrobo/machinekit,unseenlaser/machinekit,jaguarcat79/ILC-with-LinuxCNC,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,araisrobo/machinekit,EqAfrica/machinekit,strahlex/machinekit,bmwiedemann/linuxcnc-mirror,cnc-club/linuxcnc,unseenlaser/machinekit,araisrobo/linuxcnc,ianmcmahon/linuxcnc-mirror,narogon/linuxcnc,Cid427/machinekit,cdsteinkuehler/linuxcnc,bmwiedemann/linuxcnc-mirror,araisrobo/machinekit,RunningLight/machinekit,RunningLight/machinekit,aschiffler/linuxcnc,strahlex/machinekit,mhaberler/machinekit,kinsamanka/machinekit,Cid427/machinekit,kinsamanka/machinekit,ArcEye/MK-Qt5,araisrobo/linuxcnc,araisrobo/machinekit,kinsamanka/machinekit,strahlex/machinekit,aschiffler/linuxcnc,unseenlaser/linuxcnc,Cid427/machinekit,cdsteinkuehler/MachineKit,mhaberler/machinekit,araisrobo/linuxcnc,ArcEye/machinekit-testing,kinsamanka/machinekit,ArcEye/machinekit-testing,bmwiedemann/linuxcnc-mirror,strahlex/machinekit,ArcEye/MK-Qt5,bobvanderlinden/machinekit,cnc-club/linuxcnc,strahlex/machinekit,bobvanderlinden/machinekit,bobvanderlinden/machinekit,unseenlaser/machinekit,araisrobo/machinekit,bmwiedemann/linuxcnc-mirror,araisrobo/linuxcnc,cdsteinkuehler/MachineKit,RunningLight/machinekit,EqAfrica/machinekit,cnc-club/linuxcnc,ianmcmahon/linuxcnc-mirror,RunningLight/machinekit,cdsteinkuehler/linuxcnc,aschiffler/linuxcnc,bmwiedemann/linuxcnc-mirror,mhaberler/machinekit,aschiffler/linuxcnc,narogon/linuxcnc,unseenlaser/linuxcnc,ikcalB/linuxcnc-mirror,cdsteinkuehler/linuxcnc