[PATCH] move xattr permission checks into the VFS

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From: Christoph Hellwig <hch@lst.de>

The xattr code has rather complex permission checks because the rules are very
different for different attribute namespaces.  This patch moves as much as we
can into the generic code.  Currently all the major disk based filesystems
duplicate these checks, while many minor filesystems or network filesystems
lack some or all of them.

To do this we need defines for the extended attribute names in common code, I
moved them up from JFS which had the nicest defintions.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Dave Kleikamp <shaggy@austin.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>