Adding LSA_OPENSECRET (-> LsarOpenSecret) and LSA_QUERYSECRET

Adding LSA_OPENSECRET (-> LsarOpenSecret) and LSA_QUERYSECRET
(-> LsarQuerySecret) on client side, including rpcclient command
"querysecret" for others to play with.

The major obstacle is working out the encryption algorithm used
for the secret value. It definitely uses the NT hash as part of the
key, and it seems the block size is 64 bits - probably DES based -
but I can't work out what's done in between. Help required.