* Option to build ldpc_cuda was remaining in the build script
* Build script option to build ldpc_cuda was still used in CI
* Mentions of ldpc_cuda were remaining in the documentation
Note: In the documentation, the example of ldpctest usage that was
loading ldpc_cuda was replaced by an example in which it is loading
ldpc_orig even though this is pointless as it makes ldpctest compare
ldpc_orig with ldpc_orig. On the other hand, it is the only library
other than the default ldpc that uses the former interface.