libsmack: fix label validation in smack_new_label_from_path

Off-by-one length was returned from the function. This patch fixes
the regression by doing full validation for the SMACK label.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
utils: drop build dependency on libattr, introduced by 5da1a22.

Use only glibc headers for xattr functions. Use ENODATA instead of ENOATTR.
chsmack: updating to the branch master

The function smack_label_length is available as a library
function provided by libsmack. It is better to use it for
validating labels instead of redefining it in chsmack.

Signed-off-by: José Bollo <jose.bollo@open.eurogiciel.org>
Merge branch 'v1.0.x'
Merge remote-tracking branch 'rafal-krypa/issue84' into v1.0.x
Merge branch 'v1.0.x'