Add callbacks for client TLS connection establishment:

LDAP_OPT_X_TLS_CONNECT_CB and LDAP_OPT_X_TLS_CONNECT_ARG
with int (LDAP_TLS_CONNECT_CB) (LDAP *ld, SSL *ssl, SSL_CTX *ctx, void *arg)
To be called whenever the client library allocates a new SSL* handle.