lib-sieve: increase action instance count (for limit checking) only when an action is actually created.

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

Sieve script equality function implementation was wrong.

Patch by Eray Aslan.

Patch by Timo Sirainen.

Incorporated sieve_duplicate plugin into main Pigeonhole tree as a normal extension (vnd.dovecot.duplicate).
Also restructured doc dir a bit in the process.

Clang static analyzer is happy now.

Additional paths are specified by adding a sequence number (starting at 2) to the setting name.
Added support for specifying home-relative paths for sieve_before and sieve_after.
This enables administrators to specify user-specific global Sieve scripts that cannot be viewed or changed by virtual users.

Fixed segfault bug. Forgot to change Sieve SMTP API to use scriptenv in stead of script_context directly.

lib-managesieve: changed EPROTO error to EIO in ManageSieve string stream because it is apparently not known in BSD.

  - 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 change matches a similar change in Dovecot for IMAP/POP3.
Also includes other small changes that make ManageSieve match IMAP implementation a little more closely.

ManageSieve: added support for reading quoted and literal strings as a stream. Fixes support for handing large SASL responses.
Also resolves long-standing FIXME regarding the second parameter of PUTSCRIPT: it can now be a quoted string.
Includes a few small changes in the login daemon that were done in the dovecot equivalents before.

Old name is now deprecated.
Support for the even older global_script_path name for this setting is dropped.

Setting sieve_max_redirects=0 now means that redirects are prohibited rather than unlimited.
Now there is always a limit, but it can be enormous if the administrator wants to.

Message substitutions would not always cause a proper snapshot.