Explicitly mention PKCS5_PBKDF2_HMAC in EVP doc.

Signed-off-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>

doc/crypto/EVP_BytesToKey.pod

@@ -36,8 +36,8 @@ If the total key and IV length is less than the digest length and
 B<MD5> is used then the derivation algorithm is compatible with PKCS#5 v1.5
 otherwise a non standard extension is used to derive the extra data.
 
-Newer applications should use more standard algorithms such as PBKDF2 as
-defined in PKCS#5v2.1 for key derivation.
+Newer applications should use a more modern algorithm such as PBKDF2 as
+defined in PKCS#5v2.1 and provided by PKCS5_PBKDF2_HMAC.
 
 =head1 KEY DERIVATION ALGORITHM