appveyor: msvc: consider installing deps with chocolatey

[bassosimone]

Currently, I pull dependency that I prebuilt when compiling for Windows using MSVC. However, MSVC is not our main focus. The main reason why it's there is that I want the code to be portable enough that it also works with MSVC, just in case. So, it would probably be a good idea, especially for AppVeyor builds, to use chocolatey to install such binary dependencies. This would make github.com/measurement-kit/script-build-windows possibly unnecessary. Of course, this is related to #1, because the proper place where to put the installation of dependencies would probably be .appveyor.yml.