move Windows code into a module #976

Job	Run time
Clippy	13s
Test aarch64-apple-tvos	2m 54s
Test CUDA support	22s
MSRV (ubuntu-latest)	21s
Rustfmt	17s
MSRV (windows-latest)	39s
Test (stable)	28s
Test (beta)	26s
Test (nightly)	33s
Test (linux32)	38s
Test (macos)	42s
Test (aarch64-ios)	35s
Test (win32)	35s
Test (win64)	35s
Test (mingw32)	31s
Test (mingw64)	33s
Test (windows-2019)	35s
Test (windows-aarch64, windows-latest, stable, aarch64-pc-windows-msvc, --no-run)	35s
	11m 32s

Provide feedback