Improve customization of Start Menu.
JIRA issue: CORE-19494
- Add SmallStartMenu flag to TW_STRUCKRECTS2
structure.
- Add IDS_ADVANCED_SMALL_START_MENU
resource string.
- Update g_TaskbarSettings.sr.SmallStartMenu via
a callback function.
- Check g_TaskbarSettings.sr.SmallStartMenu
when Start Menu is updated.