[HTML] Fix dummy implementation of IDispatch::GetIDsOfNames().
[HTML] Fix IDocHostUIHandler::GetExternal().

It is supposed to return IDispatcha of enclosing application,
not our web browser window.
[EXPAND] Fix selecting old GDI object to DC after use.
[GRID] Fix leaking table on control destruction.
[GRID] Restore HDC by hand instead with RestoreDC().
[MDITAB] Compute desired width of an inserted item just once.
[MDITAB] Fix GDI object leak.