Add minimal CMake file for Windows

[zethon]

I put this together for a project I'm working on and thought others might find it useful.

[dreais]

nice one, thanks for the share buddy!

[unmanned-player]

Is it OK if I give a full fledged CMake build, one that supports all known platforms (minus Borland)? See my fork here: https://github.com/unmanned-player/PDCurses