Kaiju Engine (issue #32) - Get a very basic OpenGL implementation started

Adding the code for both Windows and Linux. I also updated the build scripts to include the libraries needed for compiling both Win32 and X11 for use of OpenGL. This required Glad and Glad_wgl on Windows so I copied that from one of my C game engines and also had to generate the wgl header from the glad generator. This is just doing a very basic OpenGL clear screen to cornflower blue.

https://github.com/KaijuEngine/kaiju/pull/35