Fix doc build error introduced at 30341a87
Fix doc build error introduced at 30341a87

Apparently index entries which contain underscores don't
build on Ubuntu 8.04 unless a backslash is added before
the underscore.  This is related to the way LaTeX normally
treats _ as denoting a subscript in equations.

This unfortunately adds spurious backslashes in the HTML index,
but we'll have to live with that at the moment.

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