(make-mime-entity-internal): Renamed from `make-mime-entity'.

(make-mime-entity-internal): Renamed from `make-mime-entity'.
(mime-entity-buffer-internal): New function.
(mime-entity-header-start-internal): New function.
(mime-entity-header-end-internal): New function.
(mime-entity-body-start-internal): New function.
(mime-entity-body-end-internal): New function.
(mime-entity-node-id-internal): New function.
(mime-entity-content-type-internal): New function.
(mime-entity-content-disposition-internal): New function.
(mime-entity-encoding-internal): New function.
(mime-entity-original-header-internal): New function.
(mime-entity-children-internal): New function.
(mime-entity-parsed-header-internal): New function.
(mime-entity-set-original-header-internal): Renamed from
`mime-entity-set-original-header'.
(mime-entity-set-children-internal): Renamed from
`mime-entity-set-children'.
(mime-entity-set-parsed-header-internal): Renamed from
`mime-entity-set-parsed-header'.
Move `mime-entity-SLOT' functions to mime.el.