* epg.el (epg-make-data-from-file): New function.

* epg.el (epg-make-data-from-file): New function.
(epg-make-data-from-string): New function.
(epg-data-file): New function.
(epg-data-string): New function.
(epg-start-decrypt): Get a cipher text from a data object.
(epg-delete-output-file): New function.
(epg-decrypt-file): Add the 3rd argument PLAIN to specify where
the output goes.
(epg-start-verify): Get a signature and signed-text from a data
object.
(epg-verify-file): Added the 3rd argument PLAIN to specify where
the output goes; return the plain text if PLAIN is nil.
(epg-verify-string): Return the plain text.
(epg-start-sign): Get a plain text from a data object.
(epg-sign-file): Added the 3rd argument SIGNATURE to specify where
the output goes.
(epg-start-encrypt): Get a plain text from a data object.
(epg-encrypt-file): Added the 4th argument CIPHER to specify where
the output goes.
(epg-start-import-keys): Get keys from a data object.
(epg-import-keys-1): New function.
(epg-import-keys-from-file): Use it.
(epg-import-keys-from-string): Use it.