my new clang-tidy version comes with some quite restrictive checks that fail on
current code in PQClean.

I have disabled the following three:
https://releases.llvm.org/11.0.0/tools/clang/tools/extra/docs/clang-tidy/checks/llvmlibc-restrict-system-libc-headers.html
https://clang.llvm.org/extra/clang-tidy/checks/cppcoreguidelines-init-variables.html
https://clang.llvm.org/extra/clang-tidy/checks/bugprone-reserved-identifier.html

* Add state destroy to SHA2 API

* Include optimized SPHINCS+ implementations

I've generated new implementations from the sphincsplus repository.

* Don't destroy sha256ctx after finalize

* Attempt to shut up MSVC

* Make sure to drop errors in rmtree

clang9.0.0 (https://releases.llvm.org/9.0.0/tools/clang/docs/ReleaseNotes.html)
adds a new satic analyzer: security.insecureAPI.DeprecatedOrUnsafeBufferHandling
which throws warnings if you use "unsafe" buffer handling functions which
includes memset and memcpy.
We have memset and mempy all over the place, so I think it's best to ignore this warning.
All the occurences that I looked at seemed perfectly "safe" to me.

* Ignore pointless clang-tidy warning.

It wants you to write type suffixes for integers using uppercase. Let's
just disable this warning.

https://clang.llvm.org/extra/clang-tidy/checks/readability-uppercase-literal-suffix.html

* Clean up bugprone-narrowing-conversion

Also fixes some tidy issues

Not sure why my local clang-tidy doesn't complain