Ensure MessageAppend and FlagsSet/FlagsClear have access to the username triggering the action
Enhance SSL/TLS configuration options, and apply further enhancements
from #2642 (Goetz Babin-Ebell) and #3119, #3133 (Duncan Gibbs)

Changed settings:

    ldap_tls_cacert_dir -> ldap_ca_dir
    ldap_tls_cacert_file -> ldap_ca_file
    ldap_tls_cert -> ldap_client_cert
    ldap_tls_check_peer -> ldap_verify_peer
    ldap_tls_ciphers -> ldap_ciphers
    ldap_tls_key -> ldap_client_key

    tls_ca_file -> tls_client_ca_file
    tls_ca_dir -> tls_client_ca_dir

        The paths formerly used as the CA file or directory for client SSL
        certificate verification are now specifically named as such.

    tls_cipher_list -> tls_ciphers

    tlscachedb -> tls_sessions_db
    tlscachedb_path -> tls_sessions_db_path

        While tls_sessions.db is indeed a caching database, consistency
        makes it more transparent what setting applies to what database.

New settings:

    tls_client_cert: <none>
    tls_client_key: <none>

        Client SSL certificate and key to use when cyrus-imapd behaves as
        a client (to other cyrus-imapd server (instances)).

    tls_client_ca_file: <none>
    tls_client_ca_dir: <none>

        Certificate Authority file or directory used to verify client SSL
        certificates.

    tls_client_certs: off|optional|require

        Disable, allow or require clients authenticate with an SSL
        certificate.

    tls_server_cert: <none>
    tls_server_key: <none>

        Server SSL certificate and key to use for connections from
        clients.

    tls_server_ca_file: <none>
    tls_server_ca_dir: <none>

        Certificate Authority file or directory used to verify SSL
        certificates offered by other servers.

    tls_compression: 0

        Enable TLS compression. Disabled by default.

    tls_eccurve: prime256v1

        Select the elliptic curve used for ECDHE.

    tls_prefer_server_ciphers: 0

        Prefer the cipher order configured on the server-side.

    tls_versions: ssl2 ssl3 tls1_0 tls1_1 tls1_2

        Disable SSL/TLS protocols not in this list.

Bugzilla #3822, #3830, #3843, #3861.
Prefix all configuration options related to automatic creation of mailboxes
with autocreate_*.
Fix compiler warnings
Allow suppressing autocreate functionality
Merge #3374 from worldonline/ticket/3374-master
Apply new default for unixhierarchysep (#3682)
Apply new default for expunge_mode and delete_mode (#3684, #3685)
Update the option names in cunit tests as well
From 0d80ef50 by Bron Gondwana: Bug #3390 - add 'proc_path' config variable for proc directory
Issue configuration option deprecation warnings.

Add back the deprecated options to lib/imapoptions, so we can issue the deprecation warnings.