glfw (bundled library) should be updated

[Ape]

There was an upstream issue on glfw regarding mesa drivers. Any glfw application would just refuse opening any windows.

This issue has been now fixed with the latest upstream version of glfw [1]. I propose that we update the bundled library to match this commit or any later.

[1] elmindreda/glfw@9e94577

[Ape]

There has been some minor changes to glfw API since the currently bundled versions, but the needed updates on DCPUToolchain code are just about 5 lines like this:

glfwSetWindowCloseCallback(&vm_hw_glfw_close_window_callback);
to
glfwSetWindowCloseCallback(context, &vm_hw_glfw_close_window_callback);

[jdiez17]

I'll pull the latest snapshot from @elmindreda's repo and update the API calls, thanks for the tip.