Make unpredictableSeed use CryptGenRandom (CryptoAPI) on Windows

[0xEAB]

This patch changes unpredictableSeed to call CryptGenRandom on Windows.
Analogous to #10623 (Linux).

On the one hand, the legacy CryptoAPI might be deprecated, on the other hand using it does not introduce a new DLL dependency. advapi32 is already required by std.registry and Phobos is linked against as seen in the current Makefile.
Using the more modern CNG (BCryptGenRandom) would not only introduce a new dependency, but also require us to add the corresponding bindings to druntime. I figured that wouldn’t be worth the effort for now.

[dlang-bot]

Thanks for your pull request, @0xEAB!

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Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + phobos#10624"

[0xEAB]

Blame D-Scanner for this monstrosity :)

[ichordev]

On the one hand, the legacy CryptoAPI might be deprecated, on the other hand using it does not introduce a new DLL dependency. advapi32 is already required by std.registry and Phobos is linked against as seen in the current Makefile. Using the more modern CNG (BCryptGenRandom) would not only introduce a new dependency, but also require us to add the corresponding bindings to druntime. I figured that wouldn’t be worth the effort for now.

I was pretty surprised that DRuntime didn't already have BCrypt bindings. It shouldn't be much work for me to add them. What do you think?

[thewilsonator]

What do you think?

Yes please.

[ichordev]

Yes please.

Will do.
Does anyone know where Microsoft are hiding their header files? All I managed to find is a bunch of SDK downloads which don't contain any headers upon extraction. In fact all they seem to contain is obfuscated nonsense.

EDIT: found it