NOTE: Dovecot doesn't currently MIME-encode these in the headers.

Also cleaned up the surrounding code a bit.

This way, a duplicate is only marked when the script execution succeeds, as required in the specification.

Presence of :addresses argument was represented incorrectly.

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.

lib-sieve: Fixed sieve_result_global_log_error to log only as i_info in administrator log (syslog) if executed from multiscript context.
Previously, this would work correcly only from the user's personal script and not from multiscript (sieve_before/sieve_after).

Backwards compatibility is provided for vnd.dovecot.duplicate.
Still need to fix the constraint that it must not track duplicates from failed Sieve executions.

This function now returns the binary prefix (file path until '.svbin) rather than just the path of the directory where the binary would be stored.

Some programs can be instructed to output special status information to an extra fd other than stdout or stderr.
Also added an option to drop stderr output from program to /dev/null.

lib-sieve: spamtest/virustest extensions: Tests were erroneously performed against the original message.
When used together with extprograms filter to add the spam headers, the changes were not being used by the spamtest and virustest extensions.

doc/extensions/spamtest-virustest.txt: Clarified that these extensions use the extended POSIX regular expressions.

sieve_extprograms plugin: Changed program client such that the filter command only needs to create a temporary file when the program output is very large.
This commit also includes a small change that makes it possible to run a program several times.

lib-sieve: Added method to script object for obtaining the directory where the script binary is stored.

Moved script-client from extprograms plugin to lib-sieve/util and renamed it to program-client for generic use.

In the future, much of these can be moved to Dovecot.

Sieve extprograms plugin: Fixed 'Bad filedescriptor' error occurring when disconnecting script client.

Output stream remained open, including the flush io, causing a second assert failure.
Whether this fixes the problem entirely remains to be seen.