Make tests and examples use glad

examples/wave.c

@@ -17,6 +17,7 @@
 #include <stdlib.h>
 #include <math.h>
 
+#include <glad/glad.h>
 #include <GLFW/glfw3.h>
 
 #include <linmath.h>
@@ -411,6 +412,7 @@ int main(int argc, char* argv[])
     glfwSetScrollCallback(window, scroll_callback);
 
     glfwMakeContextCurrent(window);
+    gladLoadGLLoader((GLADloadproc) glfwGetProcAddress);
     glfwSwapInterval(1);
 
     glfwGetFramebufferSize(window, &width, &height);