Fixed particles example on Retina displays.

examples/particles.c

@@ -986,11 +986,11 @@ int main(int argc, char** argv)
     glfwMakeContextCurrent(window);
     glfwSwapInterval(1);
 
-    glfwSetWindowSizeCallback(window, resize_callback);
+    glfwSetFramebufferSizeCallback(window, resize_callback);
     glfwSetKeyCallback(window, key_callback);
 
     // Set initial aspect ratio
-    glfwGetWindowSize(window, &width, &height);
+    glfwGetFramebufferSize(window, &width, &height);
     resize_callback(window, width, height);
 
     // Upload particle texture