Fix/msvc_compilation

[radekd91]

This PR enables installation of this package on Windows using MSVC compiler.

This involves two things:

1. modification of the destination folder of setup.py into which CGAL will get unzipped, because MSVC expects it in a slightly different location
2. modfiication of visibility.cpp to prevent linker errors on MSVC

The changes should not affect compilation on Linux and MacOS at all.