Make tests and examples use glad

tests/iconify.c

@@ -28,6 +28,7 @@
 //
 //========================================================================
 
+#include <glad/glad.h>
 #include <GLFW/glfw3.h>
 
 #include <stdio.h>
@@ -149,6 +150,9 @@ static GLFWwindow* create_window(GLFWmonitor* monitor)
         exit(EXIT_FAILURE);
     }
 
+    glfwMakeContextCurrent(window);
+    gladLoadGLLoader((GLADloadproc) glfwGetProcAddress);
+
     return window;
 }