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

lib-sieve: Moved handling of implicit keep during multiscript execution outside the script sequence itself.
Before, implicit keep was executed as part of the final script execution. This caused the implicit keep to be executed as part of that script, including global context.
This caused insignificant errors during delivery to be logged as errors in the administrator log when the last script is global.

sieve-filter: Fixed handling of failure-related implicit keep when there is an explicit default destination folder.
The message was left in the source mailbox, even though it was stored in the destination folder.

LDA Sieve plugin: Changed error handling so that each action log message can have up-to-date time stamps.
This change matches a change in LDA that is aimed at logging timing statistics.

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

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.

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

Change backported from Pigeonhole v0.4 tree, which means that this change will duplicate there upon merge.

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

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 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.

- Now compiles regularly without --with-unfinished-features
- Still experimental though, so be careful.
- Changed command structure a bit, removing the useless -M option.

Made vnd.dovecot.debug extension available to the LDA plugin instead of only the command line tools.