#140 Few patches from vspkg

[Mihail Naydenov]

https://github.com/microsoft/vcpkg/tree/master/ports/freeimage

Here are quite a few patches that vspkg applies to FreeImage. Most of these related to having the dependencies be external - something that FreeImage aims to avoid - but the others should be evaluated.

Other then that, vspkg comes with a nice cmake support (though, written with external dependencies in mind).