Integrate BIKE [Round2]

[mkannwischer]

if possible - otherwise document why not.

[mkannwischer]

We are working on integration into PQClean (without libraries). Let's wait for that.

[Ko-]

BIKE has updated reference implementations, although they still use the NTL and GMP libraries. On my laptop, bike-demo-test for BIKE-1-CCA at level 1 has a peak memory consumption of 246.3 KiB, which is not going to fit on our platform. The situation is exactly the same for the optimized implementation.

[mjosaarinen]

BIKE has just updated their specs to the third round and to use the standard SHA-384 and I've written an implementation that doesn't require NTL or GMP, while actually supporting all variants. So should be able to contribute an implementation if I can just find little time to adjust it for PQM4.
I'll have to double-check the memory requirement but it's a lot less than what it used to be.

[Ko-]

The spec was updated again to v4.0. Just one variant with two security levels now. The reference implementation still uses OpenSSL and NTL. @mjosaarinen any thoughts on whether your adaptions to not depend on external libraries directly carry over to v4.0?

[mkannwischer]

Fiiiiiinaaallly resolved by #175.
Thank you @devillegna!!