MSVC fixes for 4.1.1

commit d4f6f58a:

compat/windows: Add VS module definition files
These are needed for producing DLLs on Windows.

commit cfeacc59:

meson: Do not link static on Windows, use .def files
Now we can link dynamically on Windows. Linking only statically uses
>10GB of RAM while linking on my machine and causes heavy swapping.

commit d48fc69b:

meson: Set the version for libavfilter/version.h correctly
This was missed, and is obviously wrong.

commit a38bdca5:

meson: Update version.h.in from source-tree version.h
This was accidentally missed while updating.