doc/man1/x509.pod: corrected "S/MIME signing" requirements
When the "certificate purpose" is checked and KeyUsage extension is present,
either 'digitalSignature' or 'nonRepudiation' is accepted.
Manual page corrected to reflect the above.
@@ -871,8 +871,8 @@ this is because some Verisign certificates don't set the S/MIME bit.
=item B<S/MIME Signing>
-In addition to the common S/MIME client tests the digitalSignature bit must
-be set if the keyUsage extension is present.
+In addition to the common S/MIME client tests the digitalSignature bit or
+the nonRepudiation bit must be set if the keyUsage extension is present.
=item B<S/MIME Encryption>
