SDL2 improvements, and Integration of older native platform code.

[mdsitton]

I feel this is somwhat a seperate issue from issue #10 after working on this portion of the code. I realised that there are issues and missing features the SDL2 code currently in use.

A list of issues so far:
Current window size is not passed back into the window module.
Fullscreen not implemented.
No concept of monitors.
Multiple windows not implemented currently.

These are some of the ones that need to be fixed before trying to integrate the native win32 backend.

Then integration will require refactoring both to provide the same API. There are going to be many changes to both. The older display module was only ever implemented with win32, and it definitely needs some love.