example: closes win32 window properly in WGL example (#504)

Window did not respond properly to closing via the 'x' button.  Tested
on Windows 10.

Author: carsonalh

example/c/wgl.c

@@ -158,8 +158,10 @@ int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLi
 LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {
     switch (uMsg) {
     case WM_QUIT:
-    case WM_DESTROY:
     case WM_CLOSE:
+        DestroyWindow(hWnd);
+        break;
+    case WM_DESTROY:
         PostQuitMessage(0);
         break;
     default: