lib-sieve: Cleaned up command argument definitions using newer C99 syntax.

src/lib-sieve/ext-encoded-character.c

src/lib-sieve/plugins/body/tst-body.c

src/lib-sieve/plugins/copy/ext-copy.c

src/lib-sieve/plugins/date/tst-date.c

src/lib-sieve/plugins/duplicate/tst-duplicate.c

src/lib-sieve/plugins/editheader/cmd-addheader.c

src/lib-sieve/plugins/editheader/cmd-deleteheader.c

src/lib-sieve/plugins/enotify/cmd-notify.c

src/lib-sieve/plugins/imap4flags/tag-flags.c

src/lib-sieve/plugins/include/cmd-include.c

src/lib-sieve/plugins/index/tag-index.c

src/lib-sieve/plugins/mailbox/tag-mailbox-create.c

src/lib-sieve/plugins/mime/cmd-break.c

src/lib-sieve/plugins/mime/cmd-foreverypart.c

src/lib-sieve/plugins/mime/tag-mime.c

src/lib-sieve/plugins/notify/cmd-denotify.c

src/lib-sieve/plugins/notify/cmd-notify.c

src/lib-sieve/plugins/notify/ext-notify-common.c

src/lib-sieve/plugins/spamvirustest/tst-spamvirustest.c

src/lib-sieve/plugins/vacation/cmd-vacation.c