Clang -Wvargargs complained about passing a bool argument to va_start().

perl -i -pe 's/unsigned int ([^,:;]+):1;/bool $1:1;/' **/*.[ch]

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

Doveadm-sieve plugin may be broken at this point; not tested so far.

Added support for the :optional tag of the include command.
Changed Sieve script API in the process; opening the script is now available as a separate step.

  - 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.

Enforced ManageSieve protocol syntax better with some of the commands; some commands still allowed spurious extra arguments.

- Administrators now get properly notified about uncompiled global scripts and the inability of the sieve plugin to store global binaries.
- Improved binary load/save error handling and fixed a few smal bugs.
- Simplified ManageSieve error handling.