Linux 3.19 rc4

Another week, another -rc.

Things have remained reasonably calm, although we also had a few
last-minute MM regressions. Happily, most of them got fixed really
quickly, with one remaining arm64 issue still pending.

So go forth and test some more. I'll be traveling for the next two
weeks due to LCA, but I should have internet, and if things continue
to be reasonably calm I don't think that my travel should be all that
noticeable. Finally the timing worked out, unlike several releases
last year.

Anyway, the appended shortlog gives the details, but apart from the
kgdb patches showing up as some uncommon work under kernel/debug/,
things look fairly normal: mostly driver updates (gpu, pinctrl, hid,
networking), architecture updates (mainly x86 this time, some minor
arm[64] stuff), and some tooling fixes (mainly perf).