Kernel prepatch 5.19-rc2

The second 5.19 kernel prepatch is out fortesting.

And yes, because I expected the rc2 week to be fairly quiet, I dida system update on my workstation, and as a result I spent a day ortwo then sorting out most of the fallout from the resultingcompiler upgrade to gcc-12. Some of it ended up being a bitheavy-handed, and we'll be tweaking things further. And some of itends up being an actual compiler misfeature.