(rmail-narrow-to-non-pruned-header): Deleted.

(rmail-narrow-to-non-pruned-header): Deleted.
(rmail-unknown-mail-followup-to, rmail-retry-failure): No longer
call rmail-narrow-to-non-pruned-header and replace
mail-fetch-field with rmail-header-get-header because that one
ignores the intangible property when searching.
(rmail-show-message): Simplify x-coding-system handling.
(rmail-redecode-body): No longer call rmail-header-show-headers
because rmail-header-get-header handles the intanglible property.
(rmail-reply): Simplify code at the price of some efficiency when
setting up the variable bindings.  No longer toggle visibility of
headers, because rmail-header-show-headers is no longer necessary.