Removed implicit glfwMakeCurrentContext.

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

examples/splitview.c

@@ -467,12 +467,13 @@ int main(void)
         exit(EXIT_FAILURE);
     }
 
+    // Enable vsync
+    glfwMakeContextCurrent(window);
+    glfwSwapInterval(1);
+
     glfwGetWindowSize(window, &width, &height);
     windowSizeFun(window, width, height);
 
-    // Enable vsync
-    glfwSwapInterval(1);
-
     // Enable sticky keys
     glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);