opengl: disable vsync

This way I can better watch how changes affect FPS/frame times, rather than have it capped at
60FPS/16.6ms
Does not introduce visible tearing.

The engine runs at about 170 FPS on my Tesla M40, and so does minecraft. It never goes past that, I think this is a
limitation of using prime offloading. Runs at 300FPS on average on the Radeon HD6850 to which I
normally offload the Tesla to

src/main.cpp

@@ -44,6 +44,7 @@ int main()
         return -1;
     }
     glfwMakeContextCurrent(window);
+    glfwSwapInterval(0);
 
     if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
     {