bug#11496: 24.1.50; Line numbers are not redrawn correctly in linum-mode

[martin rudalics]

> Start with emacs -Q.
> Don't maximize frame.
> Open a file that has more lines than the current frame.
> M-x linum-mode
> Maximize frame.
> Line numbers are only drawn where the original, visible frame boundary
> was.
> Press down arrow key.
> Line numbers are redrawn for the entire frame.

A trivial bug: linum should run `linum-after-config' when the window
configuration changes.

> The same thing happens when narrowing on a function and then widen
> again.  Only the narrowed piece has the new line numbers until the next
> explicit redraw.

That's a different issue.

martin