Make MAIL_INDEX_MAIL_FLAG_BACKEND visible to mail_get_flags() and allow it to be changed.
Make MAIL_INDEX_MAIL_FLAG_BACKEND visible to mail_get_flags() and allow it
to be changed.

--HG--
branch : HEAD

jkerihuel/dovecot,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot,jkerihuel/dovecot,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jkerihuel/dovecot