The LDAP code in libcurl can't handle LDAP servers of LDAPv3 nor binary
attributes in LDAP objects. So, I made a quick patch to address these
problems.

The solution is simple: if we connect to an LDAP server, first try LDAPv3
(which is the preferred protocol as of now) and then fall back to LDAPv2.
In case of binary attributes, we first convert them to base64, just like the
openldap client does. It uses ldap_get_values_len() instead of
ldap_get_values() to be able to retrieve binary attributes correctly. I
defined the necessary LDAP macros in lib/ldap.c to be able to compile
libcurl without the presence of libldap