在Create之前调用SetSplitterExtendedStyle方法, 增加SPLIT_FIXEDBARSIZE风格, 就是用预设的宽度,而不获取滚动条的宽度
m_wndSplitter.SetSplitterExtendedStyle(SPLIT_FIXEDBARSIZE);
m_hWndClient = m_wndSplitter.Create(m_hWnd, rcDefault, NULL, WS_CHILD | WS_VISIBLE | WS_CLIPSIBLINGS | WS_CLIPCHILDREN);