Merge branch 'stable/for-jens-3.16' of...

Merge branch 'stable/for-jens-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip into for-3.16/drivers

Konrad writes:

Please git pull the following branch:

git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git stable/for-jens-3.16

which has a bunch of fixes to the Xen block frontend and backend driver
and a new parameter for Xen backend driver - an override (set by the toolstack)
whether to expose the discard support (if disk of course supports it) or not.