This makes this available for other extensions.

These will influence some of the performed tests.

doveadm sieve plugin: Added proper handling of Sieve storage initialization failure occurring when sieve_enabled=no

This allows completely disabling Sieve processing for a particular user.

It now extracts bare text from HTML/XHMTL parts.
Other text/* parts are still returned as is. Any other unrecognized content types are skipped.

This allows setting the MAIL FROM of the SMTP envelope for the notification e-mails.
The syntax is identical to the sieve_redirect_envelope_from setting.

lib-sieve: Created generic implementation for parsing an envelope_from setting, such as sieve_redirect_envelope_from.
Also adds a new source for the envelope_from address called "postmaster". This means that the value is obtained from the postmaster_address LDA setting.

lib-sieve: script storage: Sieve mailbox attributes use an external storage, so they don't need to be synced explicitly with any mail storage backend.
Patch by Timo Sirainen.

doveadm sieve plugin: Fixed crashes caused by incorrect context allocation in the command implementations.
The base context struct was allocated, rather than the (larger) command-specific context.
Patch by Timo Sirainen.

This makes sure that the resulting mail storage events are of the correct type for logging/notification.

This causes link failures for certain platforms.

Sieve extprograms plugin: Made line endings configurable for the input passed to the external program.

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