Removed implicit glfwMakeCurrentContext.

Implicitly making the context current makes sense in a
single-window API but less sense in a multi-window one.

examples/wave.c

@@ -413,11 +413,12 @@ int main(int argc, char* argv[])
         exit(EXIT_FAILURE);
     }
 
+    glfwMakeContextCurrent(window);
+    glfwSwapInterval(1);
+
     glfwGetWindowSize(window, &width, &height);
     window_size_callback(window, width, height);
 
-    glfwSwapInterval(1);
-
     glfwSetInputMode(window, GLFW_KEY_REPEAT, GL_TRUE);
 
     // Initialize OpenGL