Renamed CMS_RESPONSE.call_..hook with invoke_..._hook
Renamed CMS_HOOK_VALUE_ALTER as CMS_HOOK_VALUE_TABLE_ALTER
Renamed CMS_HOOK_MENU_ALTER as CMS_HOOK_MENU_SYSTEM_ALTER
Added new CMS_HOOK_MENU_ALTER that acts on CMS_MENU object.
Cosmetic, comments.
