Add a BCrypt abstraction

This is an issue that surfaced in the uuid project, where seed_rng does not work with UWP non-desktop.  To support newer Windows platforms, the random project will need access to bcrypt.  BCrypt will be used by future boostorg/random for all platforms at Windows 7 or later in the random_device code.  BCrypt is also available in MinGW-x64, but it is not available in MinGW.