* wl-draft.el (wl-draft-insert-from-field): Use (length "From: ")

* wl-draft.el (wl-draft-insert-from-field): Use (length "From: ")
instead of magic-number 6.  Use `not' instead of `null' for symbol
`nil' check (not empty list).
(wl-draft-insert-x-face-field): Fixed paren style.

* wl-draft.el (wl-draft-insert-x-face-field-here): Use `when' for
one-branch conditional statement, instead of `and' and `if'.
(wl-draft-forward): Likewise.
(wl-draft-add-references): Likewise.
(wl-draft-yank-from-mail-reply-buffer): Likewise.

* wl-draft.el (wl-draft-delete-myself-from-cc): Refactoring nested
conditional steatment.  Use `cond' instead of `if'.
(wl-draft-confirm): Likewise.