factor out selection of docbuilding packages
factor out selection of docbuilding packages

this depends on the distribution version, not the kernel version,
so this arrangement makes more sense

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