lib-sieve: Implemented sieve_redirect_envelope_from setting, which allows configuring the envelope sender of redirected messages.
Can either be set to the envelope sender, recipient, or orignal recipient of the processed message or it can be set explicitly to a static address.

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

Reported by Coverity.

Parallel to identical Dovecot change.

A va_copy creates a initialised va_list, as if a va_start had been done on it.
Therefore, pedantically, a va_end should also be done on it. On most platforms
this is a no-op, and for those where it isn't, the pairing is important.

This change matches parallel change in Dovecot. Also signalled by Coverity.

SMTP API now supports adding multiple recipients to a single SMTP transaction. This makes enotify/notify more efficient, since only one message is actually sent.

Patch by Timo Sirainen (modified).

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

Also contains a few other small fixes by Timo.

Before, sievec and sieve-dump would switch to mail_uid:mail_gid and then fail to compile/dump a root script.

Added test for interaction between include extension and dict script location support.

Patch by Timo Sirainen.

Clang static analyzer is happy now.

  - 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 is needed for the new extprograms plugin.

This puts the ".sieve" and ".svbin" file extension definitions in a single locatio.
IMPORTANT: this fixes a bug in the include extension that implicitly mapped script names like "name.sieve" to "name".

- Added sieve_global_extensions setting.

Configuration is now only read once at extension initialization.