libsmack: fixed label validation in smack_have_access()

This patch adds subject and object validation to smack_have_access().
It also validates that labels are at most 23 characters when only
short labels are available.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
utils: fix error message in smackaccess

perror() reports success when validation fails. This patch makes
the error message explicit. Invalid input is the most probable case.
Also, error message is prefixed with the basename of the utility.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Merge remote-tracking branch 'jsakkine/issue83' into v1.0.x

Conflicts:
	libsmack/libsmack.c