File Labeling Changes
Motivation: Re-use xattr API and support included in 2.5.
Reworked LSM hooks and added xattr handlers to support use of
xattr by security modules (in 2.5).
Changed SELinux to use xattr when available.
Added hooks and devpts xattr handler to support setting
security labels on ptys (in 2.5).
Added hook to support /proc/pid inode security labeling based
on associated task (in 2.5).