Before, actions were executed and committed in full after each script in a
sequence. With this change, actions can still be rolled back until the end of
all Sieve script and action execution.

The committed flag is set when at least one action was committed successfully.
The existing executed flag is repurposed to signal successful execution of at
least one action. These flags are now also properly managed for the keep action.

It is no longer used.

Adds status parameter to sieve_result_execute().

This indicates whether the last script in the sequence is being executed.

Before it always used the name of the action definition, which is confusing e.g.
for the keep and fileinto actions, which both map to the same "store" action
definition.

This allows logging action messages through a different (child) event.

Dovecot core doesn't have copyright notices in header files.

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

lib-sieve: multiscript: Fixed bug in handling of (implicit) keep; final keep action was executed as though there was a failure.
Among other things, this caused the keep action to revert back to the initial message, causing editheader actions to be ignored.

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.

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

Added means to log user errors/warnings as info in master log.
Previous change was inadequate because an error was still logged.

Patch by Timo Sirainen.

This is needed for the new extprograms plugin.