[PATCH v4 0/3] cgroup: add xattr support

This series are a refreshed version of a patchset submitted by Li Zefan back
in march:
	https://lkml.org/lkml/2012/3/1/13

With Li's permission, I refreshed the patches to apply over the latest upstream
and added the modifications suggested by others in the thread:
- using a mount option instead of config option to enable the xattr support
- reinitialize the list in kmem_xattrs_free()
- renamed functions to simple_xattr_*()

v4:
- implemented requested changes by Tejun Heo in patch #2

Signed-off-by: Li Zefan <lizefan <at> huawei.com>
Signed-off-by: Aristeu Rozanski <aris <at> redhat.com>