Wgl is implemented using the regular DllImport + delegate approach, in
order to support extensions. The delegates have not been armed at this
point, so we need to use the DllImport directly.
The whole wgl API should be revisited (we are using only a tiny
portion.)
This is a new platform that can be used then sdl2 is installed on the target system. SDL2 is commercially supported by Valve and provides better support for MacOS compared to our current implementation (Cocoa vs Carbon). It will also help us introduce faster support for new platforms. Existing platforms remain as a fallback and will be automatically used if sdl2 is not installed.
Please note that this is still a work in progress. The new mouse and keyboard API is not supported yet. Due to limitations of sdl2, multiple mice/keyboards are also not supported.
