Stribog: change endianness of the final result

* cipher/stribog.c: change endianness of the hash result.
* tests/basic.c (check_digests): adapt Stribog tests.
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Stribog standard (GOST R 34.11-2012) is a bit vague on the
representation of the final result. This mistake is supported by GOST
signatures being not so clear on the endianness of the hash value.
Fix the Stribog result endianness to fully confirm to standard.
This is proven by a (draft) publication of PBKDF2 test cases done by
TC26.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Add Stribog OIDs from TC26 space

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Add PBKDF2 tests for Stribog512

* tests/t-kdf.c (check_pbkdf2): Add Stribog512 test cases.
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TC26 published a draft of PKCS#5 GOST extension containing test vectors
for using Stribog512 in PBKDF2 scheme.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>