Mimics Dovecot/IMAP change 1001bda65e9f592d852a26ddd6a993f7973050bf.

This allows completely disabling Sieve processing for a particular user.

Passed NULL as reason to client_disconnect(), which is not allowed.

managesieve: Managesieve used "managesieve" rather than "sieve" as login service name, which means that all managesieve-specific settings where ignored.

Nobody does that, but we support it.

lib-sieve: storage: Added parameter to sieve_script_delete() to allow ignoring the active status of the script.
Normally, the active script cannot be deleted.
This change is necessary to handle doveadm sieve delete -a correctly when the provided script is the default.

This allows performing ManageSieve actions at command line or through doveadm server.

Changed handling of ENOSPACE to a normal temporary failure and added handling of ENOQUOTA as a user error.
Patch by Timo Sirainen.

Doveadm-sieve plugin may be broken at this point; not tested so far.

Most important change is that mail service_user was not freed.

Parallel to identical Dovecot change for imap and pop3.

This change is bigger than I would have liked, so this needs to be tested more.

Sieve storage now updates sieve attributes in the user's INBOX if used by ManageSieve.

Patch by Timo Sirainen.

Added flag to prevent warnings about non-link active scripts and disable critical error logging.
A rather fundamental synchronization problem remains to be solved.

http://dovecot.org/patches/2.2/doveadm-sieve-plugin.diff
Made some small modifications.
This code should not interfere with normal ManageSieve operation, so I commit this right now without much testing.
The actual doveadm sieve plugin has a few open issues that need to be resolved still.

Added support for the :optional tag of the include command.
Changed Sieve script API in the process; opening the script is now available as a separate step.

Also contains a few other small fixes by Timo.

lib-managesieve: changed EPROTO error to EIO in ManageSieve string stream because it is apparently not known in BSD.

  - Built generic interface for alternative script sources.
  - Implemented dict script location.
  NOTE: ManageSieve will not work with this yet, nor will sieve_before/sieve_after.

This change matches a similar change in Dovecot for IMAP/POP3.
Also includes other small changes that make ManageSieve match IMAP implementation a little more closely.

ManageSieve: added support for reading quoted and literal strings as a stream. Fixes support for handing large SASL responses.
Also resolves long-standing FIXME regarding the second parameter of PUTSCRIPT: it can now be a quoted string.
Includes a few small changes in the login daemon that were done in the dovecot equivalents before.