Added glx.h to OpenGL.h and commented out a return statement.

[Snoucher]

glx.h helps with linux compilation, without it the functions glXGetCurrentContext and glXGetCurrentDisplay in raytracer.c don't get recgonised.

Also I commented out a return false; because it was inside a void function.

With these changes, I was able to compile the game on my linux machine. There are some things still need working on, like OpenCL-ICD-Loader just gives me headaches when trying to compile, but that's not this repo's problem :)