Require `mmgnus'.

Require `mmgnus'.
(mail-header-subject): Now an alias for
`mime-gnus-entity-subject-internal'.
(mail-header-set-subject): Now an alias for
`mime-gnus-entity-set-subject-internal)'.
(mail-header-from): Now an alias for `mime-gnus-entity-from-internal'.
(mail-header-set-from): Now an alias for
`mime-gnus-entity-set-from-internal'.
(mail-header-date): Now an alias for `mime-gnus-entity-date-internal'.
(mail-header-set-date): Now an alias for
`mime-gnus-entity-set-date-internal'.
(mail-header-message-id): Now an alias for
`mime-gnus-entity-id-internal'.
(mail-header-id): Likewise.
(mail-header-set-message-id): Now an alias for
`mime-gnus-entity-set-id-internal'.
(mail-header-set-id): Likewise.
(mail-header-references): Now an alias for
`mime-gnus-entity-references-internal'.
(mail-header-set-references): Now an alias for
`mime-gnus-entity-set-references-internal'.
(mail-header-chars): Now an alias for
`mime-gnus-entity-chars-internal.
(mail-header-set-chars): Now an alias for
`mime-gnus-entity-set-chars-internal.
(mail-header-lines): Now an alias for
`mime-gnus-entity-lines-internal'.
(mail-header-set-lines): Now an alias for
`mime-gnus-entity-set-lines-internal'.
(mail-header-xref): Now an alias for `mime-gnus-entity-xref-internal'.
(mail-header-set-xref): Now an alias for
`mime-gnus-entity-set-xref-internal'.
(make-full-mail-header): New implementation [use `luna-make-entity'].
(make-full-mail-header-from-decoded-header): Likewise.