Removed implicit glfwMakeCurrentContext.

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

tests/modes.c

@@ -143,9 +143,11 @@ static void test_modes(void)
             continue;
         }
 
-        glfwSetTime(0.0);
+        glfwMakeContextCurrent(window);
         glfwSwapInterval(1);
 
+        glfwSetTime(0.0);
+
         while (glfwGetTime() < 5.0)
         {
             glClear(GL_COLOR_BUFFER_BIT);