Fix checkboxed treeview selection display.
JIRA issue: CORE-19480
- Make the first argument of TREEVIEW_ToggleItemState non-const.
- Select the item by calling TREEVIEW_SelectItem in TREEVIEW_ToggleItemState.
Remove WM_SYSKEYDOWN handling at component level, in consistency with other components (ListView,...)
Early embodiement of the fix proposed to WineHQ : https://bugs.winehq.org/show_bug.cgi?id=49097 in order to remove functionnal limitation in ReactOS. CORE-17020