Caused by recent event API changes.

This reduces the number of log functions for the error handler from four to just
one.

lib-sieve: lexer: Adjusted to Dovecot change: i_stream_get_data() no longer returns NULL when returned size = 0.

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.

- 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.

Enforced limits on string length and handled the finite nature of integers for number parsing and the construction of the AST.