Emit sectionHidden(int, bool) signal when QHeaderView section become hidden/shown

When a header section is resized, the sectionResized() signal is emitted. It would be nice if a corresponding signal, sectionHidden(int logicalIndex, bool hidden) for example, was emitted when a header section becomes hidden or shown. This could happen for example when hideSection() is called or if a section is resized so it becomes 0 wide, or if it is resized from 0 width to something visible.