Add LDAP constants

[haszi]

I did not write any descriptions for the peer certificate checking and CRL evaluation strategy constants as I could not find any references discussing these in detail.

Peer certificate checking strategies:
LDAP_OPT_X_TLS_ALLOW
LDAP_OPT_X_TLS_DEMAND
LDAP_OPT_X_TLS_HARD
LDAP_OPT_X_TLS_NEVER
LDAP_OPT_X_TLS_TRY

CRL evaluation strategies:
LDAP_OPT_X_TLS_CRL_ALL
LDAP_OPT_X_TLS_CRL_NONE
LDAP_OPT_X_TLS_CRL_PEER

[Girgias]

Maybe @MCMic can provide some desriptions?

[haszi]

I've found this page where it is suggested that the TLS_REQCERT (and presumably the TLS_CRLCHECK) sections of this manpage are what we're looking for here. Unfortunately I don't know enough about LDAP to be sure.

[Girgias]

I'll wait a bit longer, if @MCMic doesn't reply we'll merge as is.

[haszi]

I've read up some more on LDAP and added the descriptions for peer certificate and CRL evaluation strategies.

References:

• client (TLS_REQCERT and TLS_CRLCHECK)
• server (TLSVerifyClient and TLSCRLCheck)

[kocsismate]

@Girgias Do you think we can merge it now? If all LDAP constants are going to be documented then only ~170 globals constants remain undocumented (on global constant pages at least). That's brilliant work! 👏