openldap-server: enable crypt(3) passwords

openldap-server: enable crypt(3) passwords

With crypt(3) password storage scheme enabled, OpenLDAP can receive and
store SHA-256 and SHA-512 password hashes from Samba AD-DC. Without
crypt(3), synchronization of passwords between Samba AD-DC (v4.5 and
above) and OpenLDAP requires use of cleartext passwords.

To use password hashes from Samba, OpenLDAP must be compiled with
--enable-crypt switch. This patch introduces a new configuration
parameter to enable the use of crypt(3) function by OpenLDAP.

Enabling crypt(3) increases the size of slapd binary by 12 bytes on
the x86_64 target and by only 4 bytes on the ipq806x target.

Signed-off-by: Val Kulkov <val.kulkov@gmail.com>