Support for `schannel.h` and `wincrypt.h` functions

Is anyone currently working on adding support for the win32 functions needed to establish a TLS connection? Is this the appropriate place to add them, or would they belong in a separate package?

The need here is that I would like to write a library analogous to Rust's `native-tls` crate, which uses the system-native TLS implementation on as many platforms as possible. This is preferred in some cases over bundling a TLS implementation with the application, because it can receive security updates and enhancements without intervention from the application's maintainer. Moreover, it allows the application to respect system-wide configuration, like the set of trusted root CA's.

This is a feature request, but if nobody else is working on it or wants to work on it, I can do it When I Have Spare Time (TM).

Start by reviewing how this Haskell Win32 package organizes Windows API support and whether schannel.h and wincrypt.h belong here or in a separate package. Define the Win32 functions needed to establish a native TLS connection and verify that the resulting support can provide system-native TLS configuration for a library analogous to Rust's native-tls.

Written by the indexing model from the issue text.