Wine Mono vagrant build environment

[Vincent Povirk]

I'm not sure if anyone will care about this, but I figured I should
mention it somewhere.

With the release of Wine Mono 4.7.0 today, the source tree now ships
with a Vagrantfile, which can be used with Vagrant to create a virtual
machine that can build the project. This was the environment used to
create the msi package, and I plan to continue using it this way for
future releases.

Previously, the official build environment was my work PC, which means
there was always the possibility that upgrading or changing it would
have some effect on the official packages.

I don't know if this is useful for anyone else, but I figure that an
easy way to create a build environment, along with the complete
documentation of that environment which we get as a side-effect, can
only be a good thing.

This is not a replacement for building on real hardware. I only plan
to use it to make official builds, not for development, and I still
want to hear about any issues people encounter while trying to do the
build on their own systems.