Allow use of nistp256/384/521 keys in authorized_keys file. (#9)
Allow use of nistp256/384/521 keys in authorized_keys file. (#9)

This patch allows to use this pam module with NIST ECC keys in
user .ssh/authorized_keys file. Only 256, 384 and 521 field
lengths are supported (same as allowed in ssh-keygen -t ecdsa).
OpenSC/pam_p11,OpenSC/pam_p11