Make partly compilable in Linux

Fix typo in CMakeList.txt

Is now compilable under mingw

Compilable without afx

GL: Add GetMainDC()

JWnd: Make some window functions const

Make usable for CMake

GL: Also link to Glu32.lib

GL: Make sure aspect ratio is correct

GL: Add SwapBuffers() and handle window resize

JWnd: Add RunLoop() function to run the default message loop

GL: Create render context

JWnd: Fix compile error

Beginnings of JOpenGL

JWnd: Use WndInit struct (with lots of defaults) to initialize a window