'MIME-encapsulated blind carbon copy' based on Nakayama-san's implementation.

'MIME-encapsulated blind carbon copy' based on Nakayama-san's implementation.

* wl-vars.el (wl-draft-mime-bcc-field-name): New user option.
(wl-draft-mime-bcc-body): Ditto.

* wl-draft.el (wl-draft-setup): Setup wl-draft-mime-bcc-field-name.
(wl-message-mail-p): Added wl-draft-mime-bcc-field-name.
(wl-draft-dispatch-message): Call wl-draft-mime-bcc-field and
wl-draft-do-mime-bcc.
(wl-draft-mime-bcc-field): New function.
(wl-draft-do-mime-bcc): Ditto.

* wl-address.el (wl-address-complete-header-list): New variable.
(wl-address-complete-header-regexp): Changed default value.