methods :
 - EVP_PBE_scrypt
 - EVP_PKEY_meth_add0
 - EVP_PKEY_meth_new
 - EVP_PKEY_CTX_dup
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NBernd Edlinger <bernd.edlinger@hotmail.de>
Reviewed-by: NMatthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/5783)

Building without the scrypt KDF is now possible, the OPENSSL_NO_SCRYPT
define is honored in code. Previous this lead to undefined references.
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NStephen Henson <steve@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4116)

Add an interface that allows accessing the scrypt KDF as a PKEY_METHOD.
This fixes #4021 (at least for the scrypt portion of the issue).
Reviewed-by: NPaul Dale <paul.dale@oracle.com>
Reviewed-by: NStephen Henson <steve@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4026)