- 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.

Fixes behavior of body test with multipart MIME body parts.
Testsuite needs to be extended accordingly.

Updated version number to v0.4.0 and added a warning to configure.
Applied generic-login.patch.

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.

This is needed for the new extprograms plugin.

Removes quite a bit of duplicated source code.

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".

This is borrowed from Dovecot's lib-storage/index/maildir.