fix rmail armor decryption problems

* lisp/mail/rmail.el (rmail-epa-decrypt): Don't decrypt an armor
that was copied into the message from a message it is a reply to.
(rmail-epa-decrypt-1): Catch and ignore errors in
epa-decrypt-region.  Make armor-start and armor-end markers.
1 job for master in 54 minutes and 7 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #896
test-all

00:54:07