v3.5.1

• securedht: certificates are now stored at the sha256 of their public key (instead of the sha1). This enables certificate lookup by sha256 of the public key. Lookup by sha1 is still supported but deprecated.
• build/cmake: major improvements to the Windows/MSVC build (@twdragon, @novemus)
• build/cmake: properly set exported symbols when building a shared library
• build/cmake: add presets
• build: add vcpkg support on Windows
• Fix use of gnutls library on Windows