Correct EVP_SealInit() documentation, iv is an output

=head1 DESCRIPTION

The EVP envelope routines are a high level interface to envelope

encryption. They generate a random key and then "envelope" it by

using public key encryption. Data can then be encrypted using this

key.

encryption. They generate a random key and IV (if required) then

"envelope" it by using public key encryption. Data can then be

encrypted using this key.

EVP_SealInit() initializes a cipher context B<ctx> for encryption

with cipher B<type> using a random secret key and IV supplied in

the B<iv> parameter. B<type> is normally supplied by a function such

as EVP_des_cbc(). The secret key is encrypted using one or more public

keys, this allows the same encrypted data to be decrypted using any

of the corresponding private keys. B<ek> is an array of buffers where

the public key encrypted secret key will be written, each buffer must

contain enough room for the corresponding encrypted key: that is

with cipher B<type> using a random secret key and IV. B<type> is normally

supplied by a function such as EVP_des_cbc(). The secret key is encrypted

using one or more public keys, this allows the same encrypted data to be

decrypted using any of the corresponding private keys. B<ek> is an array of

buffers where the public key encrypted secret key will be written, each buffer

must contain enough room for the corresponding encrypted key: that is

B<ek[i]> must have room for B<EVP_PKEY_size(pubk[i])> bytes. The actual

size of each encrypted secret key is written to the array B<ekl>. B<pubk> is

an array of B<npubk> public keys.

The B<iv> parameter is a buffer where the generated IV is written to. It must

contain enough room for the corresponding cipher's IV, as determined by (for

example) EVP_CIPHER_iv_length(type).

If the cipher does not require an IV then the B<iv> parameter is ignored

and can be B<NULL>.

EVP_SealUpdate() and EVP_SealFinal() have exactly the same properties

as the EVP_EncryptUpdate() and EVP_EncryptFinal() routines, as 

documented on the L<EVP_EncryptInit(3)|EVP_EncryptInit(3)> manual