The newer API (Windows 10 and newer) allows the allocator to ask for
strongly aligned memory.
This is enabled only if the `WINVER` macro is set to target Windows 10
or newer. There is now a CMake option to target older versions of
Windows, so we can test both code paths.
The Azure Pipelines config now includes a test of the compatibility
version. This runs only the release build, because it's mainly there as
a sanity check - 99% of the code is the same as the default Windows
config.
