For screen savers and lockers other than Xscreensaver, this should work to suspend the screen saver when you're using software that doesn't do it for you. For example, games running in WINE. You just run it in a terminal and leave it.
Code:
watch -n 30 xset s reset
"xset s reset" works by calling XResetScreenSaver, and "watch -n 30" runs it every 30 seconds. This is literally identical, on a calls-to-X level, to how SDL does it.