Windows build with Msys2/MinGW64

[vryy]

It seems that the instruction to compile on Windows (see #26) is outdated. I looked at INSTALL_WINDOWS and saw the line numbers are not correct anymore. Also, in sc.h and p4est_algorithms.c there is code like defined _WIN32. So is the native build with Visual Studio supported or still experimental?

[sloede]

I don't know about native builds using VS, but note that we still build p4est regularly using MinGW as part of Julia's BinaryBuilder stack (such that p4est is available as a library in Julia without user compilation).

This is essentially the build script being used, maybe it can be of use for you to get started:
https://github.com/JuliaPackaging/Yggdrasil/blob/494a78263c891933191a3c6308420036a243357d/P/P4est/build_tarballs.jl#L19-L65