imap-login: Move ID command handling to its own file.

Updated copyright notices to include the year 2018.

*-login: Remove unnecessary ssl-proxy.h include

*-login: Use io_add_istream() instead of io_add()

global: start relying on timeout_remove(NULL) being a no-op Cleanup performed with the following semantic patch: @@ expression E; @@ - if (E != NULL) { - timeout_remove(&E); - } + timeout_remove(&E);

*-login: Add client_vfuncs.free() that is called when client refcount=0 This can be useful for plugins that want to run something after proxying ends. Use an empty default function so plugins can call super.free() without having to check if it's NULL.

imap-login: Fix storing ID NIL values into client_id

imap-login: Fix crash in ID if trusted client sends NIL value to internal field Fixes: Panic: imap-login: file imap-login-client.c: line 215 (cmd_id_handle_keyvalue): assertion failed: (client_id_str == !client_id_reserved_word(key))

*-login: Add client_vfuncs.input_next_cmd() This allows plugins to hook into all the pre-login commands. For example with imap-login most of the commands could already be hooked into, except for ID and AUTHENTICATE because their parameters reading is handled specially. This allows hooking into them as well. This is actually internal to all the login binaries, so it wouldn't have to be in login-common. However, login-common already has all the code to handle overriding functions nicely and this is a rather useful feature for all the protocols anyway, so it's easier this way and not too ugly.

*-login: Add client_vfuncs.send_raw_data() This allows login plugins to hook into seeing all the data that is sent to the imap/pop3 client.

*-login: Minor logging cleanup if client is disconnected before sending banner. Avoid unnecessarily adding "(no auth attempts in 0 secs)" when the reason string already makes it clear that the user didn't even have a chance to authenticate. This kind of disconnection currently happens only with some plugins.

imap-login: Retain client ID only when enabled

imap-login: Move forward_fields updating code to login-common This allows using the new client_add_forward_field() in e.g. plugins.

imap-login: Allow x-forward- to specify forward fields from trusted networks

imap-login: Retain ID request without dovecot specials

imap-login: Log proxy state as human-readable string. Separate sent/received state and log them as strings.

Updated copyright notices to include the year 2017.

imap-login: Skip NIL value in ID handler NIL value can cause hard crash, depending what the key is. For x-proxy-ttl, NIL will crash on any system, x-originating-ip will crash on some nss versions (e.g. centos 6.7). Migitating factor here is that the NIL value is only accepted from trusted network.

imap: Implemented support for the LITERAL- capability. This replaces the LITERAL+ capability when the imap_literal_minus setting is enabled.

lib-imap: imap-parser: Turned the fatal error flag into a proper error code.

imap-login: Renamed client.[ch] to imap-login-client.[ch] This allows installing the imap-login-client.h without conflicting.