DH subgroup order (q) (#3369)
* Support DH q (subgroup order)
* Change RFC5114.txt to NIST format
* Add tests for DH q
* Update docs for DH q
* Fix pep8
* Improve test covergae for DH q
* Create _dh_params_dup that copy q if DHparams_dup don't
On OpenSSL < 1.0.2 DHparams_dup don't copy q. _dh_params_dup
call DHparams_dup and if the version is smaller than 1.0.2
copy q manually
* Copy q manually on libressl
* Add to test vectors serialized RFC5114 2048 bit DH parameters with 224 bit subgroup
* Support serialization of DH with q
* Add tests for serialization of DH with q
* Support DH serialization with q only if Cryptography_HAS_EVP_PKEY_DHX is true
* Raise exception when trying to serialize DH X9.42 when not supported
* raise unsupported key type when deserilizing DH X9.42 if not supported
* pep8 fixes
* Fix test_serialization
* Add dhx_serialization_supported method to DHBacked
* document q in dh_parameters_supported
* Rename dhx_serialization_supported to dh_x942_serialization_supported
20 files changed