Trace_log variable was not initialized.

This way, imapsieve can show to which user.mailbox.uid the trace applies.

Registering conflicting commands before conflicts are checked is a bad idea.
Make sure conflicting extensions are not part of remaining validation process.

This was duplicated between the lda-sieve and imapsieve plugins.

lib-sieve: Implemented support for writing runtime trace output to a directory if it exists, much like Dovecot rawlog.

doc/example-config: Added description for a few generic settings that were only mentioned in the INSTALL file.

Futher changes are needed to prevent accessing the envelope in the first place.

It allows sending feedback report (RFC 5965) messages.

lib-sieve: Notify extensions about whether they are loaded in the validator optionally (ihave extension).

Conflicts are now always tested from both sides. This is mainly important for the "ihave" test.

An earlier change exposed this bug. Before, it was always a socket, and closing the output early meant using shutdown() rather than close().
This bug caused an assert failure.

lib-sieve: Renamed sieve_runtime_flags to sieve_execute_flags and made these available to result execution.

lib-sieve: util: Fixed message header composition functions to turn newlines into proper header line continuations.

lib-sieve: redirect action: Made mail loop detection more robust by forcibly adding a Message-ID header if it is missing.

Struct mail_vfuncs has an additional method now.

This is needed for other extensions that manipulate flags while the imap4flags extension is not used directly.

This prevents a conflict between the message coming through a mailing list and a copy of that message recieved directly.
If both of these have the same message ID, one of these messages would be discarded (or worse: delivered locally) when redirected.

The caller will normally handle this and it will handle it better with more context information.
This also produced a spurious "script not found" error message when an entry but no attribute existed for an LDAP-based Sieve script.

lib-sieve: ldap storage: Clarified "script not found" errors a bit so that it is clear at which stage it occurrs.

lib-sieve: util: program-client-local: Changed link between parent and child process from a socketpair to a double pipe.

Turns out /dev/stdin, /dev/stdout, and /dev/fd/XX don't work on Linux if the underlying FD is a socket.
Since some programs may rely on those symbolic links to work, the local client is amended to use two pipes instead.
This will not help for programs invoked in the remote script service, since a socket is required for the connection.