libsmack: fix a bug in validation of labels
libsmack: fix a bug in validation of labels

The function `get_label` didn't handle the characters below
' ' and above '~' correctly.

Signed-off-by: José Bollo <08496fd66cc394b517cafa0b18bcb9ce79fe4230@open.eurogiciel.org>

jobol/smack,smack-team/smack,smack-team/smack,jobol/smack