[WINLOGON] SASWindowProc(): Call PostQuitMessage(0) on WM_DESTROY

Now the WinMain() message loop correctly exits and we get to perform
last-time cleanup. However, the main thread must not exit (except under
certain conditions, not yet implemented), so we Sleep for an infinite
amount of time.

base/system/winlogon/sas.c

@@ -1542,6 +1542,7 @@ SASWindowProc(
         {
             if (!GetSetupType())
                 UnregisterHotKeys(Session, hwndDlg);
+            PostQuitMessage(0);
             return TRUE;
         }
         case WM_SETTINGCHANGE:

base/system/winlogon/winlogon.c

@@ -614,6 +614,7 @@ WinMain(
     CleanupNotifications();
 
     /* We never go there */
-
+    // TODO: Shutdown if we are in session 0, otherwise let the process terminate.
+    SleepEx(INFINITE, FALSE);
     return 0;
 }