When sigma0 runs on a lower priority than the rest of the threads in the system
it might come to the point that while answering a page fault or I/O memory area
request the timeslice of the caller (core-pager) gets fully consumed. As long as
other threads are still executable and don't block sigma0 won't do progress
anymore, because it runs at the lowest priority. This commit simply sets
sigma0's priority to the highest in the system.
Was: 'sigma0_prio.patch'
