* (mime-pgp-bad-signature-post-function-pgp50-us): New function.

* (mime-pgp-bad-signature-post-function-pgp50-us): New function.
(mime-verify-application/pgp-signature): Say "Checking signature..." before
verifying; say "Can't check signature" if public key is not available.
(mime-pgp-parse-verify-error): Goto beginning of buffer, eval forms and set
window start.
(mime-pgp-parse-verify-error-for-pgp): Use it
(mime-pgp-parse-verify-error-for-pgp50): Use it.
(mime-pgp-parse-verify-error-for-gpg): Use it.
(mime-pgp-check-signature): Rewrite for detecting "BAD signature".
(mime-pgp-bad-signature-post-function): New macro.
(mime-pgp-bad-signature-regexp): New macro.
(mime-pgp-bad-signature-regexp-alist): New user option.