mail_index_ext_register(): Allow registering an extension without record or header. It can still be used to register expunge/sync handlers.
mail_index_ext_register(): Allow registering an extension without record or
header. It can still be used to register expunge/sync handlers.

damoxc/dovecot,damoxc/dovecot,damoxc/dovecot,damoxc/dovecot,damoxc/dovecot