This patch marks QED images as clean periodically when it is safe to do so. This reduces the chance of having to perform a consistency check at startup. Previously we left the image dirty even when it was consistent, therefore risking an unnecessary consistency check after crash.
The first patch just stubs out qemu-timer.c functions for qemu-tool.c, which is needed since block drivers get built into qemu-img and friends. I don't know the timers code well so please suggest alternatives if simple stubbing is wrong.
