lib-imap-client: Fix hang when imapc_client_get_capabilities() is called without connection

lib-imap-client: Make command tag counter externally accessible This allows unit tests to reset it.

lib-imap-client: Call the public login callback exactly once. Previously it was also called only once, as long as there were only a single imap connection. (The current imapc code wouldn't create more than one connection.) It was a bit confusing what the expectation was, so now the callback is never called more than once.

lib-imap-client: Add login_callback setter This way it can be set before actually calling login which might happen some time later.

lib-imap-client: Add imapc_client_try_stop

imapc: Use LOGOUT to cleanly disconnect from server. This makes it clearer in the remote server's logs whether the disconnection was intentional or not. Use a hardcoded 5 second timeout for LOGOUT. It should be enough time for the server to finish sending the tagged reply.

lib-imap-client: add callback to notify consumers about state changes Add a callback to notify imapc users about failures. Currently, the only failure defined is "authentication failed".

lib-imap-client: Removed unused pending_box_command_count

imapc: Avoid sending unnecessary IDLEs that are immediately aborted.

Array API changed: ARRAY_DEFINE(name, type) -> ARRAY(type) name Easy way to update your existing code: perl -i -pe 's:ARRAY_DEFINE\(([^,]+), *([^)]+)\);:ARRAY($2) $1;:' **/*.[ch]

imapc: Try to avoid crashes on deinit/disconnection.

imapc: Support retrying some IMAP commands if we get disconnected.

imapc: Initial support for automatically reconnecting to remote server.

imapc: Removed unused "stop now" functionality.

imapc: Command sending API changed to be more extensible.

Moved imapc-client into its own lib-imap-client library.