Golang LDAP client

It's a wrapper for C++ LDAP client (GCO), that supports Kerberos SASL GSSAPI.

Used as a temporary implementation in the absence of a pure Go library.

As a potential option for a future replacement, is being considered https://github.com/go-ldap/ldap, therefore, the names of functions and structures were borrowed from there, for easier transition in the future.