Fix GCM documentation: the tag does not have to be supplied before
decrypting any data any more.
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4231)
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, taglen, tag);
Sets the expected tag to B<taglen> bytes from B<tag>. This call is only legal
-when decrypting data and must be made B<before> any data is processed (e.g.
-before any EVP_DecryptUpdate() call).
+when decrypting data.
=head1 CCM Mode