Needed for adding a per-mailbox event in later commit.

Use named initializers and list the items on a separate line each.

lib-sieve: plugins: include: ext-include-binary - Properly check whether binary dependency block load succeeded.

Otherwise, a segfault may occur on a corrupt binary.

The sieve_binary_block_index/get() functions return NULL when the block index is
invalid somehow. This was not handled by the dumper, thereby causing a crash.

Problem reported by scan-build.

lib-sieve: plugins: imap4flags: test-hasflag - Fix segfault occurring for command without arguments.

This is a corner case that doesn't happen in practice, but it can be created in
the test suite.