GOST provider

The GOST provider is currently built in parallell with the GOST engine, and is implemented like a wrapper around the engine code.

Currently implemented

Symmetric ciphers:

gost89
gost89-cnt
gost89-cnt-12
gost89-cbc
kuznyechik-ecb
kuznyechik-cbc
kuznyechik-cfb
kuznyechik-ofb
kuznyechik-ctr
magma-cbc
magma-ctr
magma-ctr-acpkm
magma-ctr-acpkm-omac
kuznyechik-ctr-acpkm
kuznyechik-ctr-acpkm-omac

Hashes:

id-tc26-gost3411-12-256 (md_gost12_256)
id-tc26-gost3411-12-512 (md_gost12_512)
id-GostR3411-94 (md_gost94)

MACs:

gost-mac
gost-mac-12
magma-mac
kuznyechik-mac
kuznyechik-ctr-acpkm-omac

TODO, not requiring additional OpenSSL support

Basic support for GOST keys, i.e. implementations of KEYMGMT (including key generation), DECODER and DECODER.
Support for these operations using GOST keys:
- ASYM_CIPHER (encryption and decryption using GOST keys)
- SIGNATURE (signing and verifying using GOST keys)

TODO, which requires additional OpenSSL support

TLSTREE support. This may require additional changes in libssl. Needs investigation.
PKCS7 and CMS support. This requires OpenSSL PKCS7 and CMS code to change for better interfacing with providers.

TODO, far future

Refactor the code into being just a provider. This is to be done when engines aren't supported any more.