Linux 5.0 rc4

Another week, another release candidate - this time from home.

Nothing particularly stands out, except for the fact that the bulk of
the pull requests came in late in the week. Which worked out ok, if
only because it meant I could do a fair chunk of them on my main
machine rather than on my laptop.

And that "most pull requests come in Friday-Saturday" is a pretty
common pattern, so it's not like it's worrisome. People push their
work for the week to me, and/or just target making the next rc.
Whatever the reason, things look pretty normal, and nothing huge
stands out.

Size-wise, rc4 has a bit more commits that the last few releases have
had at this point, but it's not even remotely a new record size, and
not all that much of an outlier anyway. I _do_ hope that things will
start to calm down for rc5 onwards.

All the other statistics look pretty normal too: a bit more than half
the patch is drivers (networking, sound, tty, usb, gpu, scsi,
binderfs, you name it). With the rest being arch updates (x86, arm,
arc) headers, some library fixes, core networking and kernel. And some
selftest updates, but the tooling changes are much smaller than they
were the last couple of rc's.

So everything looks ok. Shortlog appended for people who want to skim
the details.

Go test and report any oddities you can find, but I think we're doing fine.