Mono: fix url and add libgdiplus

Per conversion: https://github.com/Homebrew/homebrew/pull/34955. This PR fixes the `monolite` url and adds the missing `libgdiplus`.

As for `gtk-sharp`, `gtk-quartz-engine` and `mono-tools`, I haven't got them working yet. Some due to upstream bug, other for missing dependencies. 

There should be another missing libraries for mono runtime too. But I'm not familiar to mono. And there're so many libraries under https://github.com/mono. I don't which should be put into mono runtime.