Kernel prepatch 4.9-rc3

The 4.9-rc3 prepatch is out. "Itturns out that the bug that we thought was due to the new virtually mappedstacks during the rc2 release wasn't due to that at all, but a blockrequest queuing race condition. So people who turned off the new featureweren't actually avoiding it at all." The new feature appears to besolid, but more testing is always welcome.