Support GOST 2012 256 with botan

[gecheim]

In these commits the following changes:

• Fix build with CMake
• Added support CMake build with static botan library
• Added support work with GOST R 34.10 2012 256 keys with botan backend.

Issue #404

[rijswijk]

Thank you for the PR; I gave it a quick review, I saw some changes in the OpenSSL code base as well, the PR suggests it is only for Botan, do I see correctly that these are only there to make the code path for getGOSTType(..) complete? If so, is this the right approach since it seems GOST 2012 is not actually supported with OpenSSL?

I will also ask @halderen for a more detailed review.

[gecheim]

Yes, changes in OpenSSL code base support only getGOSTType(..) otherwise the project would not build with the OpenSSL backend.

OpenSSL support GOST 2012 with engine.

These changes were made for a task where you only need to work with the botan backend. So the other option was not supported in this pull request.

[atribolt]

We have the same problem. We need to work with keys like Gost2012-256 using botan. Could you apply this patch to support working with botan? But for Gost 2012 with openssl, create a separate issue.