Fixed two multi-window bugs.

src/window.c

@@ -388,11 +388,11 @@ GLFWAPI GLFWwindow glfwOpenWindow(int width, int height, int mode)
         return NULL;
     }
 
+    memset(window, 0, sizeof(_GLFWwindow));
+
     window->next = _glfwLibrary.windowListHead;
     _glfwLibrary.windowListHead = window;
 
-    memset(window, 0, sizeof(_GLFWwindow));
-
     // Set up desired framebuffer config
     fbconfig.redBits        = Max(_glfwLibrary.hints.redBits, 0);
     fbconfig.greenBits      = Max(_glfwLibrary.hints.greenBits, 0);
@@ -697,13 +697,13 @@ GLFWAPI void glfwCloseWindow(GLFWwindow window)
 
     _glfwPlatformCloseWindow(window);
 
-    free(window);
-
     prev = &_glfwLibrary.windowListHead;
     while (*prev != window)
         prev = &((*prev)->next);
 
     *prev = window->next;
+
+    free(window);
 }