merge: upstream fixes (mutt/default)

 * Change "allow_dups" into a flag at hash creation.
 * Filter expired local certs for OpenSSL verification.
 * Plug memory leak in weed-expired-certs code.
 * Fix potential cert memory leak in check_certificate_by_digest().
 * Show SHA1 fp in interactive cert check menu.
 * Prevent null pointer exception for h->ai_canonname

closes #413