[PATCH] selinux: extend selinuxfs context interface

This patch extends the selinuxfs context interface to allow return the
canonical form of the context to userspace.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>