I stole some of it from `epa-decrypt-armor-in-region' because
`epa-mail-decrypt' is interactive-only.

Ideally armor-start and armor-end should only be lexically bound, so
they should be in the let form:

(let ((buffer (get-buffer-create
		 (format "%s *decrypted*"
			 (file-name-nondirectory file))))
      armor-beg armor-end)
   ...)

--
Jamie