Linux 3.18 rc2

Another week, another rc - and now the merge window is *definitely* closed.

I had hoped that the rc1 release would mean that a few stragglers
would quickly surface, and then the rest of the rc would be more
normal. But no, I had straggling merge-window pull requests come in
all week, and rc2 is bigger than I'd like.

Oh well. It's not like I'm hugely surprised, but it does mean that I'm
probably going to be unpleasant next week to anybody who tries to get
me to pull things that I think looks like "development" rather than
"fixes". You've been warned. I effectively gave you a full three
weeks of merge window, now it's time for bugfixes, and not random
other noise. Ok?

And to be honest, we've had bigger rc2's in history. Not recently,
though. Both 3.3 and 3.4 had big -rc2 releases, and 3.15 (which was
the largest release ever, iirc) came reasonably close.

At least _part_ of the size is the very long-delayed overlayfs merge
that I already mentioned in the rc1 release message as being pending.
Let's see how much fallout that all causes, but it's been around for a
long time (partly because it needed various vfs-layer things to
integrate cleanly), and I think it's in good shape. Knock wood.

So at least partially as a result of that overlayfs merge, about a
third of the patch is filesystems. It's not _just_ overlayfs, though,
there was a late ext4 merge request that I think is actually bigger,
at least partly due to some extent handling refactoring.

The rest is the more usual driver updates (thermal, watchdog, scsi
target, ACPI & PM, misc other updates) and architecture updates (arc,
arm, powerpc, mips, x86). Some Documentation and include file updates
rounds out the rest.

Shortlog appended for details, I think it's still well within the
mailing list size constraints.