Add conditional compilation of forward compat. glfw window hint to fix crash on later versions of OSX

examples/opengl3_example/main.cpp

@@ -20,6 +20,9 @@ int main(int, char**)
     glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
     glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
     glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
+#if __APPLE__
+    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
+#endif
     GLFWwindow* window = glfwCreateWindow(1280, 720, "ImGui OpenGL3 example", NULL, NULL);
     glfwMakeContextCurrent(window);
     gl3wInit();