Kernel prepatch 5.2-rc4

The 5.2-rc4 kernel prepatch is out for
testing. 'We've had a fairly calm release so far, and on the whole that seems to
hold. rc4 isn't smaller than rc3 was (it's a bit bigger), but rc3 was
fairly small, so the size increase isn't all that worrisome. I do hope
that we'll start actually shrinking now, though.'